fix(rtc): correct join_response attribute access in FAST reconnect

`ConnectionManager._connect_internal` stores `join_response.data` as
`self.join_response` (see `connection_manager.py:387`), so credentials
live at the top level. `_reconnect_fast` was reading
`self.join_response.data.credentials.token`, which raises
`AttributeError: 'JoinCallResponse' object has no attribute 'data'`
the first time a FAST reconnect actually runs.

This codepath was never exercised before because nothing triggered a
reconnect on signaling-WS loss; with the prior commit on this branch
finally driving into `ReconnectionManager`, the latent bug surfaces.

Drop the spurious `.data` hop.

Author: aliev

getstream/video/rtc/reconnection.py

@@ -209,10 +209,13 @@ async def _reconnect_fast(self):
                 self.connection_manager._connection_options.fast_reconnect = True
                 previous_ws_client = self.connection_manager.ws_client
 
-                # Use _connect_internal with existing connection info
+                # Use _connect_internal with existing connection info.
+                # `self.join_response` is already the unwrapped data payload
+                # (see ConnectionManager._connect_internal: it stores
+                # `join_response.data`), so credentials live at the top level.
                 await self.connection_manager._connect_internal(
                     region=self.connection_manager._connection_options.region,
-                    token=self.connection_manager.join_response.data.credentials.token
+                    token=self.connection_manager.join_response.credentials.token
                     if self.connection_manager.join_response
                     else None,
                     session_id=self.connection_manager.session_id,