Remove redundant overloads from IO (#12570)

Author: srittau

stdlib/typing.pyi

@@ -800,18 +800,12 @@ class IO(Iterator[AnyStr]):
     def writable(self) -> bool: ...
     @abstractmethod
     @overload
-    def write(self: IO[str], s: str, /) -> int: ...
-    @abstractmethod
-    @overload
     def write(self: IO[bytes], s: ReadableBuffer, /) -> int: ...
     @abstractmethod
     @overload
     def write(self, s: AnyStr, /) -> int: ...
     @abstractmethod
     @overload
-    def writelines(self: IO[str], lines: Iterable[str], /) -> None: ...
-    @abstractmethod
-    @overload
     def writelines(self: IO[bytes], lines: Iterable[ReadableBuffer], /) -> None: ...
     @abstractmethod
     @overload