chore: update wa-v2 service name

Author: apaparazzi0329

ibm_watson/assistant_v2.py

@@ -49,7 +49,7 @@ class AssistantV2(BaseService):
     """The Assistant V2 service."""
 
     DEFAULT_SERVICE_URL = 'https://api.us-south.assistant.watson.cloud.ibm.com'
-    DEFAULT_SERVICE_NAME = 'conversation'
+    DEFAULT_SERVICE_NAME = 'assistant'
 
     def __init__(
         self,