Rollup merge of #111592 - Nemo157:fix-vec-capacity-examples, r=joshtriplett

Change Vec examples to not assert exact capacity except where it is guaranteed

It was [brought up on discord](https://discord.com/channels/273534239310479360/818964227783262209/1107633959329878077) that the `Vec::into_boxed_slice` example contradicted the `Vec::with_capacity` docs in that the returned `Vec` might have _more_ capacity than requested.

So, to reduce confusion change all the `assert_eq!(vec.capacity(), _)` to `assert!(vec.capacity() >= _)`, except in 4 examples that have guaranteed capacities: `Vec::from_raw_parts`, `Vec::from_raw_parts_in`, `Vec::<()>::with_capacity`,`Vec::<(), _>::with_capacity_in`.

library/alloc/src/vec/mod.rs

@@ -646,14 +646,14 @@ impl<T, A: Allocator> Vec<T, A> {
     ///
     /// // The vector contains no items, even though it has capacity for more
     /// assert_eq!(vec.len(), 0);
-    /// assert_eq!(vec.capacity(), 10);
+    /// assert!(vec.capacity() >= 10);
     ///
     /// // These are all done without reallocating...
     /// for i in 0..10 {
     ///     vec.push(i);
     /// }
     /// assert_eq!(vec.len(), 10);
-    /// assert_eq!(vec.capacity(), 10);
+    /// assert!(vec.capacity() >= 10);
     ///
     /// // ...but this may make the vector reallocate
     /// vec.push(11);
@@ -877,7 +877,7 @@ impl<T, A: Allocator> Vec<T, A> {
     /// ```
     /// let mut vec: Vec<i32> = Vec::with_capacity(10);
     /// vec.push(42);
-    /// assert_eq!(vec.capacity(), 10);
+    /// assert!(vec.capacity() >= 10);
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -1028,7 +1028,7 @@ impl<T, A: Allocator> Vec<T, A> {
     /// ```
     /// let mut vec = Vec::with_capacity(10);
     /// vec.extend([1, 2, 3]);
-    /// assert_eq!(vec.capacity(), 10);
+    /// assert!(vec.capacity() >= 10);
     /// vec.shrink_to_fit();
     /// assert!(vec.capacity() >= 3);
     /// ```
@@ -1055,7 +1055,7 @@ impl<T, A: Allocator> Vec<T, A> {
     /// ```
     /// let mut vec = Vec::with_capacity(10);
     /// vec.extend([1, 2, 3]);
-    /// assert_eq!(vec.capacity(), 10);
+    /// assert!(vec.capacity() >= 10);
     /// vec.shrink_to(4);
     /// assert!(vec.capacity() >= 4);
     /// vec.shrink_to(0);
@@ -1090,7 +1090,7 @@ impl<T, A: Allocator> Vec<T, A> {
     /// let mut vec = Vec::with_capacity(10);
     /// vec.extend([1, 2, 3]);
     ///
-    /// assert_eq!(vec.capacity(), 10);
+    /// assert!(vec.capacity() >= 10);
     /// let slice = vec.into_boxed_slice();
     /// assert_eq!(slice.into_vec().capacity(), 3);
     /// ```