Rollup merge of rust-lang#115454 - vwkd:patch-1, r=scottmcm

Clarify example in docs of str::char_slice

Just a one word improvement.

“Last” can be misread as meaning the last (third) instead of the previous (first).

library/core/src/str/mod.rs

@@ -808,7 +808,7 @@ impl str {
     /// assert_eq!(Some((0, 'y')), char_indices.next()); // not (0, 'y̆')
     /// assert_eq!(Some((1, '\u{0306}')), char_indices.next());
     ///
-    /// // note the 3 here - the last character took up two bytes
+    /// // note the 3 here - the previous character took up two bytes
     /// assert_eq!(Some((3, 'e')), char_indices.next());
     /// assert_eq!(Some((4, 's')), char_indices.next());
     ///