stubtest: warn about missing __del__ (#16456)

Fixes #16414

Author: hauntsaninja

mypy/stubtest.py

@@ -1381,7 +1381,6 @@ def verify_typealias(
         "__annotations__",
         "__text_signature__",
         "__weakref__",
-        "__del__",  # Only ever called when an object is being deleted, who cares?
         "__hash__",
         "__getattr__",  # resulting behaviour might be typed explicitly
         "__setattr__",  # defining this on a class can cause worse type checking