Apply suggestions from code review

Co-authored-by: Jubilee <[email protected]>

Author: ChrisJefferson

library/std/src/path.rs

@@ -1169,7 +1169,6 @@ impl FusedIterator for Ancestors<'_> {}
 /// path.push(r"..\otherdir");
 /// path.push("system32");
 ///
-/// path.set_extension(r"\..\temp");
 #[cfg_attr(not(test), rustc_diagnostic_item = "PathBuf")]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct PathBuf {
@@ -1456,8 +1455,6 @@ impl PathBuf {
     /// If the file stem contains internal dots and `extension` is empty, part
     /// of the old file stem will be considered the new [`self.extension`].
     ///
-    /// The new `extension` is not sanitized, so may include separators.
-    ///
     /// See the examples below.
     ///
     /// [`self.file_name`]: Path::file_name
@@ -1487,9 +1484,6 @@ impl PathBuf {
     ///
     /// p.set_extension("");
     /// assert_eq!(Path::new("/feel/the"), p.as_path());
-    ///
-    /// p.set_extension("/darkest.cookie");
-    /// assert_eq!(Path::new("/feel/the./darkest.cookie"), p.as_path());
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn set_extension<S: AsRef<OsStr>>(&mut self, extension: S) -> bool {