Draft: Change allow_iframes_in_markdown FF from wip to gitlab_com_derisk

Asherah Connorrequested to merge
push-ryoqstxnuktq into master

What does this MR do and why?

Promotes the allow_iframes_in_markdown FF from wip to gitlab_com_derisk.

For merging after Support iframe embeds in rich-text editor (#596744 - closed) is complete.

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