string: remove stray comment (#8329)

stdlib/string.pyi

@@ -46,7 +46,6 @@ class Template:
         def get_identifiers(self) -> list[str]: ...
         def is_valid(self) -> bool: ...
 
-# TODO(MichalPokorny): This is probably badly and/or loosely typed.
 class Formatter:
     @overload
     def format(self, __format_string: LiteralString, *args: LiteralString, **kwargs: LiteralString) -> LiteralString: ...