…n hook.

The new editor does not support the `edit_form_after_title` action hook. Because WordPress Core uses this hook to output the notice, it is not printed to the screen.

After WordPress#11604 is merged, legacy style admin notices (`<div class="notice">...notice content...</div>`) will be consumed by the Notices API and displayed. This change ensures that when WordPress#11604 is merged the privacy policy notice will appear again when editing the privacy policy page.

…orm_after_title`.

This prevents the notice from displaying twice if the notice has already been moved to the `admin_notices` hook (as would happen in https://core.trac.wordpress.org/attachment/ticket/45057/45057.diff).