Remove error log entry on clean BiDi shutdown. (#8806)

Closes #8803.
diff --git a/google/api_core/bidi.py b/google/api_core/bidi.py
index 7d3716d..1fab26b 100644
--- a/google/api_core/bidi.py
+++ b/google/api_core/bidi.py
@@ -669,9 +669,6 @@
                 exc,
             )
 
-        else:
-            _LOGGER.error("The bidirectional RPC exited.")
-
         _LOGGER.info("%s exiting", _BIDIRECTIONAL_CONSUMER_NAME)
 
     def start(self):