Rollup merge of rust-lang#89401 - owengage:master, r=joshtriplett

Add truncate note to Vec::resize

A very minor addition to the `Vec::resize` documentation to point out the `truncate` method.
When I was searching for something matching `truncate` I managed to miss it, along with some colleagues. We later found it by chance. We did find `resize` however, so I was hoping to point it out in the documentation.

Author: Manishearth

library/alloc/src/vec/mod.rs

@@ -2137,6 +2137,7 @@ impl<T: Clone, A: Allocator> Vec<T, A> {
     /// in order to be able to clone the passed value.
     /// If you need more flexibility (or want to rely on [`Default`] instead of
     /// [`Clone`]), use [`Vec::resize_with`].
+    /// If you only need to resize to a smaller size, use [`Vec::truncate`].
     ///
     /// # Examples
     ///