Fix formatting for removed lints

- Don't add backticks for the reason a lint was removed. This is almost
never a code block, and when it is the backticks should be in the reason
itself.
- Don't assume clippy is the only tool that needs to be checked for
backwards compatibility

tests/ui/deprecated.stderr

@@ -1,4 +1,4 @@
-error: lint `clippy::unstable_as_slice` has been removed: ``Vec::as_slice` has been stabilized in 1.7`
+error: lint `clippy::unstable_as_slice` has been removed: `Vec::as_slice` has been stabilized in 1.7
   --> $DIR/deprecated.rs:1:8
    |
 LL | #[warn(clippy::unstable_as_slice)]
@@ -6,73 +6,73 @@ LL | #[warn(clippy::unstable_as_slice)]
    |
    = note: `-D renamed-and-removed-lints` implied by `-D warnings`
 
-error: lint `clippy::unstable_as_mut_slice` has been removed: ``Vec::as_mut_slice` has been stabilized in 1.7`
+error: lint `clippy::unstable_as_mut_slice` has been removed: `Vec::as_mut_slice` has been stabilized in 1.7
   --> $DIR/deprecated.rs:2:8
    |
 LL | #[warn(clippy::unstable_as_mut_slice)]
    |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: lint `clippy::misaligned_transmute` has been removed: `this lint has been split into cast_ptr_alignment and transmute_ptr_to_ptr`
+error: lint `clippy::misaligned_transmute` has been removed: this lint has been split into cast_ptr_alignment and transmute_ptr_to_ptr
   --> $DIR/deprecated.rs:3:8
    |
 LL | #[warn(clippy::misaligned_transmute)]
    |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: lint `clippy::unused_collect` has been removed: ``collect` has been marked as #[must_use] in rustc and that covers all cases of this lint`
+error: lint `clippy::unused_collect` has been removed: `collect` has been marked as #[must_use] in rustc and that covers all cases of this lint
   --> $DIR/deprecated.rs:4:8
    |
 LL | #[warn(clippy::unused_collect)]
    |        ^^^^^^^^^^^^^^^^^^^^^^
 
-error: lint `clippy::invalid_ref` has been removed: `superseded by rustc lint `invalid_value``
+error: lint `clippy::invalid_ref` has been removed: superseded by rustc lint `invalid_value`
   --> $DIR/deprecated.rs:5:8
    |
 LL | #[warn(clippy::invalid_ref)]
    |        ^^^^^^^^^^^^^^^^^^^
 
-error: lint `clippy::into_iter_on_array` has been removed: `this lint has been uplifted to rustc and is now called `array_into_iter``
+error: lint `clippy::into_iter_on_array` has been removed: this lint has been uplifted to rustc and is now called `array_into_iter`
   --> $DIR/deprecated.rs:6:8
    |
 LL | #[warn(clippy::into_iter_on_array)]
    |        ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: lint `clippy::unused_label` has been removed: `this lint has been uplifted to rustc and is now called `unused_labels``
+error: lint `clippy::unused_label` has been removed: this lint has been uplifted to rustc and is now called `unused_labels`
   --> $DIR/deprecated.rs:7:8
    |
 LL | #[warn(clippy::unused_label)]
    |        ^^^^^^^^^^^^^^^^^^^^
 
-error: lint `clippy::regex_macro` has been removed: `the regex! macro has been removed from the regex crate in 2018`
+error: lint `clippy::regex_macro` has been removed: the regex! macro has been removed from the regex crate in 2018
   --> $DIR/deprecated.rs:8:8
    |
 LL | #[warn(clippy::regex_macro)]
    |        ^^^^^^^^^^^^^^^^^^^
 
-error: lint `clippy::drop_bounds` has been removed: `this lint has been uplifted to rustc and is now called `drop_bounds``
+error: lint `clippy::drop_bounds` has been removed: this lint has been uplifted to rustc and is now called `drop_bounds`
   --> $DIR/deprecated.rs:9:8
    |
 LL | #[warn(clippy::drop_bounds)]
    |        ^^^^^^^^^^^^^^^^^^^
 
-error: lint `clippy::temporary_cstring_as_ptr` has been removed: `this lint has been uplifted to rustc and is now called `temporary_cstring_as_ptr``
+error: lint `clippy::temporary_cstring_as_ptr` has been removed: this lint has been uplifted to rustc and is now called `temporary_cstring_as_ptr`
   --> $DIR/deprecated.rs:10:8
    |
 LL | #[warn(clippy::temporary_cstring_as_ptr)]
    |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: lint `clippy::panic_params` has been removed: `this lint has been uplifted to rustc and is now called `panic_fmt``
+error: lint `clippy::panic_params` has been removed: this lint has been uplifted to rustc and is now called `panic_fmt`
   --> $DIR/deprecated.rs:11:8
    |
 LL | #[warn(clippy::panic_params)]
    |        ^^^^^^^^^^^^^^^^^^^^
 
-error: lint `clippy::unknown_clippy_lints` has been removed: `this lint has been integrated into the `unknown_lints` rustc lint`
+error: lint `clippy::unknown_clippy_lints` has been removed: this lint has been integrated into the `unknown_lints` rustc lint
   --> $DIR/deprecated.rs:12:8
    |
 LL | #[warn(clippy::unknown_clippy_lints)]
    |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: lint `clippy::unstable_as_slice` has been removed: ``Vec::as_slice` has been stabilized in 1.7`
+error: lint `clippy::unstable_as_slice` has been removed: `Vec::as_slice` has been stabilized in 1.7
   --> $DIR/deprecated.rs:1:8
    |
 LL | #[warn(clippy::unstable_as_slice)]

tests/ui/deprecated_old.stderr

@@ -1,4 +1,4 @@
-error: lint `unstable_as_slice` has been removed: ``Vec::as_slice` has been stabilized in 1.7`
+error: lint `unstable_as_slice` has been removed: `Vec::as_slice` has been stabilized in 1.7
   --> $DIR/deprecated_old.rs:1:8
    |
 LL | #[warn(unstable_as_slice)]
@@ -6,19 +6,19 @@ LL | #[warn(unstable_as_slice)]
    |
    = note: `-D renamed-and-removed-lints` implied by `-D warnings`
 
-error: lint `unstable_as_mut_slice` has been removed: ``Vec::as_mut_slice` has been stabilized in 1.7`
+error: lint `unstable_as_mut_slice` has been removed: `Vec::as_mut_slice` has been stabilized in 1.7
   --> $DIR/deprecated_old.rs:2:8
    |
 LL | #[warn(unstable_as_mut_slice)]
    |        ^^^^^^^^^^^^^^^^^^^^^
 
-error: lint `misaligned_transmute` has been removed: `this lint has been split into cast_ptr_alignment and transmute_ptr_to_ptr`
+error: lint `misaligned_transmute` has been removed: this lint has been split into cast_ptr_alignment and transmute_ptr_to_ptr
   --> $DIR/deprecated_old.rs:3:8
    |
 LL | #[warn(misaligned_transmute)]
    |        ^^^^^^^^^^^^^^^^^^^^
 
-error: lint `unstable_as_slice` has been removed: ``Vec::as_slice` has been stabilized in 1.7`
+error: lint `unstable_as_slice` has been removed: `Vec::as_slice` has been stabilized in 1.7
   --> $DIR/deprecated_old.rs:1:8
    |
 LL | #[warn(unstable_as_slice)]