Restore class-decorator overload annotation for freeze_time

This was removed in f9235ae without explanation, possibly because mypy objects to the overlap under Python 3.13. But Pytype needs that to infer that the type is unchanged when a class is decorated with `@freezegun.freeze_time` (unlike mypy, which assumes class decorators, unlike function decorators, always leave the type unchanged).

Author: sfreilich

freezegun/api.py

@@ -632,6 +632,13 @@ def __init__(
         self.as_kwarg = as_kwarg
         self.real_asyncio = real_asyncio
 
+    # mypy objects to this because Type is Callable, but Pytype needs it because
+    # (unlike mypy's) its inference does not assume class decorators always leave
+    # the type unchanged.
+    @overload
+    def __call__(self, func: Type[T2]) -> Type[T2]:  # type: ignore[overload-overlap]
+        ...
+
     @overload
     def __call__(self, func: "Callable[P, Awaitable[Any]]") -> "Callable[P, Awaitable[Any]]":
         ...