Remove unused group functionality

discord/http.py

@@ -310,18 +310,6 @@ class HTTPClient:
     def logout(self):
         return self.request(Route('POST', '/auth/logout'))
 
-    # Group functionality
-
-    def start_group(self, user_id, recipients):
-        payload = {
-            'recipients': recipients,
-        }
-
-        return self.request(Route('POST', '/users/{user_id}/channels', user_id=user_id), json=payload)
-
-    def leave_group(self, channel_id):
-        return self.request(Route('DELETE', '/channels/{channel_id}', channel_id=channel_id))
-
     # Message management
 
     def start_private_message(self, user_id):