fix one more pytype issue

PiperOrigin-RevId: 753622033
Change-Id: I0612e43d82e270bd34d6ebc9f062dc92679a0dfd

Author: jzleibo

concordia/environment/unstable/engines/asynchronous.py

@@ -25,6 +25,7 @@
 from concordia.environment.unstable import engine as engine_lib
 from concordia.typing.unstable import entity as entity_lib
 import termcolor
+from typing_extensions import override
 
 
 DEFAULT_CALL_TO_MAKE_OBSERVATION = (
@@ -78,6 +79,7 @@ def make_observation(self,
     )
     return observation
 
+  @override
   def next_acting(
       self,
       game_master: entity_lib.Entity,