Ao3-7534 media category tag pages edit

[Mangooomango]

Pull Request Checklist

• [ x] Have you read "How to write the perfect pull request"?
• [x ] Have you read the contributing guidelines?
• Have you added tests for any changed functionality?
• [x ] Have you added the Jira issue number
  as the first thing in your pull request title (e.g. AO3-1234 Fix thing)
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Issue

https://otwarchive.atlassian.net/browse/AO3-7534

Purpose

What does this PR do?
Instead of always showing "You can use it to filter works and to filter bookmarks" for all Media Category tag pages, it will only show it to then filterable ones. It will show "It's a %{canonical_tag_link}." to no filters.

Testing Instructions

1. Go to Media Category tags for Theater, Anime, and Manga.
2. Check that it says "It is a canonical tag." instead of "You can use it to filter works and to filter bookmarks."
3. Go to canonical tag for different category
4. Check that it says "You can use it to filter works and to filter bookmarks."
   If you have a Jira account with access, please update or comment on the issue with any new or missing testing instructions instead.

If you have a Jira account with access, please update or comment on the issue
with any new or missing testing instructions instead.

You can remove this section if there are already full testing instructions in the Jira issue.

Credit

Mango (she/her)

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[sarken]

Hi, Mango -- welcome back!

It looks like you already have an open pull request for a First Timers Only issue: #5519, which needs action before it can be merged. We ask that each contributor only work on one First Timers Only issue, so we'd appreciate it if you would close one of these two pull requests. Once you've done that, we'll be happy to review the open pull request.

We're also still happy to set you up with Jira permissions as discussed on #5519, so please let us know if that's something you'd be interested in.

Thanks for contributing!