Keep hookspec signature; ignore ty empty-body

Author: tobiasraabe

src/_pytask/hookspecs.py

@@ -180,7 +180,7 @@ def pytask_collect_task_setup(
 @hookspec(firstresult=True)
 def pytask_collect_task(
     session: Session, path: Path | None, name: str, obj: Any
-) -> PTask | None:
+) -> PTask:  # ty: ignore[empty-body]
     """Collect a single task."""