Remove SupportsGetItem.__contains__ (#13541)

Author: srittau

stdlib/_typeshed/__init__.pyi

@@ -151,11 +151,8 @@ class SupportsKeysAndGetItem(Protocol[_KT, _VT_co]):
     def keys(self) -> Iterable[_KT]: ...
     def __getitem__(self, key: _KT, /) -> _VT_co: ...
 
-# This protocol is currently under discussion. Use SupportsContainsAndGetItem
-# instead, if you require the __contains__ method.
-# See https://github.com/python/typeshed/issues/11822.
+# stable
 class SupportsGetItem(Protocol[_KT_contra, _VT_co]):
-    def __contains__(self, x: Any, /) -> bool: ...
     def __getitem__(self, key: _KT_contra, /) -> _VT_co: ...
 
 # stable