Enable notifications during backfill

.. as per the default bridge config.

Source: f848710c01/mautrix_twitter/example-config.yamll (L147)

roles/matrix-bridge-mautrix-instagram/templates/config.yaml.j2

@@ -132,7 +132,7 @@ bridge:
     missed_limit: 1000
     # If using double puppeting, should notifications be disabled
     # while the initial backfill is in progress?
-    disable_notifications: true
+    disable_notifications: false
   periodic_reconnect:
     # Interval in seconds in which to automatically reconnect all users.
     # This can be used to automatically mitigate the bug where Instagram stops sending messages.