Backport Bugzilla 1947157: Move linux security warning content into own page

⬅️ Backport Patchset

Bookkeeping

Issue(s)

• https://bugzilla.mozilla.org/show_bug.cgi?id=1947157

Merge Request(s)

Target Channels

• Alpha
• Stable
• Legacy

Notes

9714e095 basically replaces 6ec44aaf.

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