heapq: re-export, add __about__ (#7308)

stdlib/_heapq.pyi

@@ -2,6 +2,8 @@ from typing import Any, TypeVar
 
 _T = TypeVar("_T")
 
+__about__: str
+
 def heapify(__heap: list[Any]) -> None: ...
 def heappop(__heap: list[_T]) -> _T: ...
 def heappush(__heap: list[_T], __item: _T) -> None: ...