Auto merge of #43563 - tbu-:pr_from_str_radix_panic, r=alexcrichton
Auto merge of #43563 - tbu-:pr_from_str_radix_panic, r=alexcrichton

Document the `from_str_radix` panic

CC #42034

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