gh-110180: Remove unused _PickleUsingNameMixin class from typing (#110181)

Author: AlexWaygood

Lib/typing.py

@@ -937,13 +937,6 @@ def _is_typevar_like(x: Any) -> bool:
     return isinstance(x, (TypeVar, ParamSpec)) or _is_unpacked_typevartuple(x)
 
 
-class _PickleUsingNameMixin:
-    """Mixin enabling pickling based on self.__name__."""
-
-    def __reduce__(self):
-        return self.__name__
-
-
 def _typevar_subst(self, arg):
     msg = "Parameters to generic types must be types."
     arg = _type_check(arg, msg, is_argument=True)