Rollup merge of #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.

diff --cc library/alloc/src/vec/mod.rs
Simple merge