Rollup merge of #55389 - meven:master, r=shepmaster
Rollup merge of #55389 - meven:master, r=shepmaster

Remove unnecessary mut in iterator.find_map documentation example, R…

Relates to #49098

Removes a mut that could induce newcomers to put a mut in their code that the compiler would comply about.

https://github.com/rust-lang/rust/pull/49098/files#r227422388

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