Rollup merge of #113934 - ajtribick:string-pop-remove-multibyte, r=thomcc

Multibyte character removal in String::pop and String::remove doctests

I think it would be useful to have the doctests for the `String::pop()` and `String::remove()` methods demonstrate that they work on multibyte UTF-8 sequences.

library/alloc/src/string.rs

@@ -1290,11 +1290,11 @@ pub fn truncate(&mut self, new_len: usize) {
     /// Basic usage:
     ///
     /// ```
-    /// let mut s = String::from("foo");
+    /// let mut s = String::from("abč");
     ///
-    /// assert_eq!(s.pop(), Some('o'));
-    /// assert_eq!(s.pop(), Some('o'));
-    /// assert_eq!(s.pop(), Some('f'));
+    /// assert_eq!(s.pop(), Some('č'));
+    /// assert_eq!(s.pop(), Some('b'));
+    /// assert_eq!(s.pop(), Some('a'));
     ///
     /// assert_eq!(s.pop(), None);
     /// ```
@@ -1324,11 +1324,11 @@ pub fn pop(&mut self) -> Option<char> {
     /// Basic usage:
     ///
     /// ```
-    /// let mut s = String::from("foo");
+    /// let mut s = String::from("abç");
     ///
-    /// assert_eq!(s.remove(0), 'f');
-    /// assert_eq!(s.remove(1), 'o');
-    /// assert_eq!(s.remove(0), 'o');
+    /// assert_eq!(s.remove(0), 'a');
+    /// assert_eq!(s.remove(1), 'ç');
+    /// assert_eq!(s.remove(0), 'b');
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]