Reword Buffer docs

Co-authored-by: Ralf Jung <post@ralfj.de>

Author: Jules-Bertholet

library/core/src/iter/adapters/map_windows.rs

@@ -30,8 +30,8 @@ struct MapWindowsInner<I: Iterator, const N: usize> {
     buffer: Option<Buffer<I::Item, N>>,
 }
 
-/// `Buffer` uses two times of space to reduce moves among the iterations.
-/// `Buffer<T, N>` is semantically `[MaybeUninit<T>; 2 * N]`. However, due
+/// `Buffer<T, N>` is semantically `[MaybeUninit<T>; 2 * N]`. This helps
+/// reduce moves while iterating. However, due
 /// to limitations of const generics, we use this different type. Note that
 /// it has the same underlying memory layout.
 ///