Fix last mypy issue in utils.py and activate mypy checking

Author: henrikmidtiby

manim/_config/utils.py

@@ -1459,7 +1459,7 @@ def enable_gui(self, value: bool) -> None:
         self._set_boolean("enable_gui", value)
 
     @property
-    def gui_location(self) -> tuple[Any]:
+    def gui_location(self) -> tuple[int, ...]:
         """Location parameters for the GUI window (e.g., screen coordinates or layout settings)."""
         return self._d["gui_location"]