bpo-46741: Update `asyncio.protocols.BufferedProtocol` docstring (GH-31327) (GH-31362)

The docstring for `BufferedProtocol` states that the class is still an "experimental API", but it has been considered stable since 3.8.
(cherry picked from commit 1d81fdc4c004511c25f74db0e04ddbbb8a04ce6d)

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
1 file changed