Revert security product billing docs (#476)

[maximelb]

Reverts #476. Email and Code Security will be bought by subscribing to the extension, like other extensions, rather than through a separate paid-coverage activation. Updated billing docs will follow.

🤖 Generated with Claude Code

[limacharlie-refractionpoint]

LimaCharlie Cloud Security — code scan

No new code findings were introduced by this pull request.

This check reports and never fails: no gating.fail_on is set on the code_scanning policy.

Scanned refractionPOINT/documentation 3da7c3a…79e9394 — only findings new in the head commit are listed; anything already on the base branch is the repository's own finding set, on the Cloud Security Code page.

This comment is updated in place on every push to this pull request.