fixup! Add method to check if a

Author: Marenz

src/frequenz/dispatch/_dispatcher.py

@@ -221,7 +221,7 @@ def cancel(self, msg: str | None = None) -> None:
         for instance in self._actor_dispatchers.values():
             instance.cancel()
 
-    def is_dispatching(self, dispatch_type: str) -> bool:
+    def is_managed(self, dispatch_type: str) -> bool:
         """Check if the dispatcher is managing actors for a given dispatch type.
 
         Args: