Be able to hide annotations without flagging them first

### Problem:
Currently, moderators have to go through a multi-step process to hide any annotations that haven't been flagged by users but nevertheless still need to be hidden. Moderators must:
1. Flag annotation (hit the flag icon)
2. Click Hide

An ideal flow would be that moderators (who are currently identified as group owners), would have the capability to hide any annotation they deem necessary, by simply hiding the annotation.

This feedback has come from multiple partners, and it's an issue I've been meaning to write up for a while.

Also - this is not something that needs to be figured out immediately. Just creating this so I don't lose it.

The issue names no files, tests, or entry points. Start by locating annotation moderation and the group-owner permission checks in the product code, then trace the existing flag-and-hide flow. Done means group owners can hide an unflagged annotation directly, with tests covering the permission and moderation behavior.

Written by the indexing model from the issue text.