Rollup merge of #89444 - notriddle:notriddle/contains-str, r=jyn514
Rollup merge of #89444 - notriddle:notriddle/contains-str, r=jyn514

rustdoc: use slice::contains instead of open-coding it

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