[3.9] bpo-42851: [Enum] remove brittle __init_subclass__ support (GH-24154)#24155

ethanfurman merged 1 commit intopython:3.9python/cpython:3.9from

ethanfurman:backport-a581a86-3.9ethanfurman/cpython:backport-a581a86-3.9Copy head branch name to clipboard