Firestore: Add Watch Support (#6191)

Firestore watch
diff --git a/google/api_core/bidi.py b/google/api_core/bidi.py
index 7c995c5..4d77ecc 100644
--- a/google/api_core/bidi.py
+++ b/google/api_core/bidi.py
@@ -481,7 +481,7 @@
             print(response)
 
         consumer = BackgroundConsumer(rpc, on_response)
-        consume.start()
+        consumer.start()
 
     Note that error handling *must* be done by using the provided
     ``bidi_rpc``'s ``add_done_callback``. This helper will automatically exit