docs/file_domain: remove cloudflare mention of autominify

Summary:
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
[2]: archive.today

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