Rollup merge of #56931 - pietroalbini:relnotes-1.31.1, r=pietroalbini
Rollup merge of #56931 - pietroalbini:relnotes-1.31.1, r=pietroalbini

Update release notes for Rust 1.31.1

Backport from the stable branch.

r? @ghost

aidancully/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust