Optimize unnecessary check in Vec::retain
Optimize unnecessary check in Vec::retain

Co-authored-by: oxalica <91fe0d852c19e8fed6b5af9a8eae820efccf0d79@pm.me>

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