typing correction

Author: yasserfarouk

src/negmas/sao/common.py

@@ -81,7 +81,7 @@ def negotiator_offers(self, negotiator_id: str) -> list[Outcome]:
 
 
 @lru_cache(1)
-def all_negotiator_types() -> list[SAONegotiator]:
+def all_negotiator_types() -> list[type[SAONegotiator]]:
     """
     Returns all the negotiator types defined in negmas.sao.negotiators
     """