[ObjC] Mark classes that shouldn't be subclassed as such.
Several of the classes vended by the runtime don't really support subclassing, so mark them as such to get compiler enforcement just in case. PiperOrigin-RevId: 505221732
P
Protobuf Team Bot committed
a185a6ea8a5cc1d85f8a91405a0fafd007207ca4
Parent: 55d2123
Committed by Copybara-Service <copybara-worker@google.com>
on 1/27/2023, 11:21:05 PM