Fix trailing space showing up in example

The current text is rendered as: U+005B ..= U+0060 ``[ \ ] ^ _ ` ``, or.
This patch changes that to render as: U+005B ..= U+0060 `` [ \ ] ^ _ ` ``, or

The reason for that, is that CommonMark has a solution for starting or ending inline code with a backtick/grave accent: padding both sides with a space, makes that padding disappear.

library/core/src/num/mod.rs

@@ -623,7 +623,7 @@ impl u8 {
     ///
     /// - U+0021 ..= U+002F `! " # $ % & ' ( ) * + , - . /`, or
     /// - U+003A ..= U+0040 `: ; < = > ? @`, or
-    /// - U+005B ..= U+0060 ``[ \ ] ^ _ ` ``, or
+    /// - U+005B ..= U+0060 `` [ \ ] ^ _ ` ``, or
     /// - U+007B ..= U+007E `{ | } ~`
     ///
     /// # Examples