Adds missing __dir__ definitions (#8479)

stdlib/enum.pyi

@@ -109,6 +109,7 @@ class EnumMeta(ABCMeta):
     def __members__(self: type[_EnumMemberT]) -> types.MappingProxyType[str, _EnumMemberT]: ...
     def __len__(self) -> int: ...
     def __bool__(self) -> Literal[True]: ...
+    def __dir__(self) -> list[str]: ...
     # Simple value lookup
     @overload  # type: ignore[override]
     def __call__(cls: type[_EnumMemberT], value: Any, names: None = ...) -> _EnumMemberT: ...