docs/file_domain: remove cloudflare mention of autominify
Summary:
[Auto Minify](https://developers.cloudflare.com/speed/optimization/content/auto-minify/)[1][2] is deprecated and will be removed after 2024-08-05.
(For distant future where Cloudflare deletes the docs)
[1]: [web.archive.org](https://web.archive.org/web/20240507123639/https://developers.cloudflare.com/speed/optimization/content/auto-minify/)
[2]: [archive.today](https://archive.md/wWPpM)
Signed-off-by: Yongmin Hong <revi@omglol.email>
Test Plan:
1. Wait for 2024-08-05
2. Browse to `https://dash.cloudflare.com/<account_id>/<domain>/speed/optimization/content`
3. Verify "Auto Minify" is gone
Reviewers: O1 Blessed Committers, avivey
Reviewed By: O1 Blessed Committers, avivey
Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Differential Revision: https://we.phorge.it/D25617
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