Enable invert_emails_disabled_to_emails_enabled by default

What does this MR do and why?

Enable the invert_emails_disabled_to_emails_enabled FF by default to mitigate #467690 (closed).

Moved to beta since gitlab_com_derisk FF cannot be set default_enabled as true.

Backport request: https://gitlab.com/gitlab-org/release/tasks/-/issues/11258

MR acceptance checklist

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• This MR is backporting a bug fix, documentation update, or spec fix, previously merged in the default branch.
• The MR that fixed the bug on the default branch has been deployed to GitLab.com (not applicable for documentation or spec changes).
• This MR has a severity label assigned (if applicable).
• Set the milestone of the merge request to match the target backport branch version.
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• Ensure the e2e:package-and-test-ee job has either succeeded or been approved by a Software Engineer in Test.

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