Rollup merge of #33056 - GuillaumeGomez:as_mut_ptr_example, r=steveklabnik
Rollup merge of #33056 - GuillaumeGomez:as_mut_ptr_example, r=steveklabnik

Improve as_mut ptr method example

r? @steveklabnik

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