fix: error: "ReferenceType[object]" not callable

Author: BobTheBuidler

test-data/unit/lib-stub/weakref.pyi

@@ -7,5 +7,6 @@ _T = TypeVar("_T")
 class ReferenceType(Generic[_T]):  # "weakref"
     __callback__: Callable[[Self], Any]
     def __new__(cls, o: _T, callback: Callable[[Self], Any] | None = ..., /) -> Self: ...
+    def __call__(self) -> _T: ...
 
 ref = ReferenceType