Fix empty name error message typo in bot_state.py (#345)

* Fix empty name error message typo in bot_state.py

* Update bot_state.py

Author: Kyle Delaney

libraries/botbuilder-core/botbuilder/core/bot_state.py

@@ -42,9 +42,7 @@ def create_property(self, name: str) -> StatePropertyAccessor:
         :return: If successful, the state property accessor created.
         """
         if not name:
-            raise TypeError(
-                "BotState.create_property(): BotState cannot be None or empty."
-            )
+            raise TypeError("BotState.create_property(): name cannot be None or empty.")
         return BotStatePropertyAccessor(self, name)
 
     def get(self, turn_context: TurnContext) -> Dict[str, object]: