[Auth] Remove deprecated pre-iOS 13.5 GameCenter workaround and fix force-unwrap - #16136

[Auth] Remove deprecated pre-iOS 13.5 GameCenter workaround and fix force-unwrap#16136

crleonard wants to merge 2 commits into

firebase:mainfirebase/firebase-ios-sdk:mainfrom

crleonard:fix/gamecenter-remove-pre-13-5-workaroundcrleonard/firebase-ios-sdk:fix/gamecenter-remove-pre-13-5-workaroundCopy head branch name to clipboard