Remove trailing whitespace

Co-authored-by: Mara Bos <[email protected]>

library/core/src/iter/traits/iterator.rs

@@ -469,7 +469,7 @@ pub trait Iterator {
     /// If the zipped iterator has no more elements to return then each further attempt to advance
     /// it will first try to advance the first iterator at most one time and if it still yielded an item
     /// try to advance the second iterator at most one time.
-    ///    
+    ///
     /// To 'undo' the result of zipping up two iterators, see [`unzip`].
     ///
     /// [`unzip`]: Iterator::unzip