remove pyright ignore directive for unknown variable type in test_gradual_assignment

Author: randolf-scholz

stdlib/@tests/test_cases/builtins/check_callable.py

@@ -3,4 +3,4 @@
 
 def test_gradual_assignment(arg: Any) -> None:
     if callable(arg):
-        _: int = arg()  # pyright: ignore[reportUnknownVariableType]
+        _: int = arg()