Moderation banner not shown immediately after flagging an annotation

[robertknight]

Steps to reproduce

1. Enable flag_action feature flag for users A and B
2. Create group as user A
3. Create annotation on page P in group as user B
4. Open client on page P as user A and flag the annotation
5. Reload client on page P as user A

Expected behaviour

Since user A is a group creator (and therefore moderator), they should see the moderation banner appear immediately after they flag the annotation.

Actual behaviour

The moderation banner does not appear until the user reloads the page.

Additional details

This happens because the act of flagging an annotation does not return the updated annotation and the client is not updating the flag count for the annotation itself.