Upgrade mypy to 0.990 (#9123)

stdlib/importlib/abc.pyi

@@ -179,6 +179,7 @@ if sys.version_info >= (3, 9):
             self, mode: str, buffering: int = ..., encoding: str | None = ..., errors: str | None = ..., newline: str | None = ...
         ) -> IO[Any]: ...
         @property
+        @abstractmethod
         def name(self) -> str: ...
         @abstractmethod
         def __truediv__(self, child: str) -> Traversable: ...