It was reported DKIM checks were failing for emails sent with addresses like `user@users.musicbrainz.org`
This is due to the fact such domain isn't really configured anywhere, and therefore email system doesn't provide proper DKIM signatures for it.

Since the goal is to anonymize editor's email address, and since those addresses are meant to be send-only, i propose to use `noreply@musicbrainz.org` instead.

This address already exists in the server configuration:
https://github.com/metabrainz/musicbrainz-server/blob/6d19f0852c75c526bba42e8818c0fa45703d2da7/lib/MusicBrainz/Server/Constants.pm#L293

Changes are required in https://github.com/metabrainz/musicbrainz-server/blob/6d19f0852c75c526bba42e8818c0fa45703d2da7/lib/MusicBrainz/Server/Email.pm#L56

And https://github.com/metabrainz/musicbrainz-server/blob/56ad625786fdf801bd943d0e4a900215ede8f8e7/t/lib/t/MusicBrainz/Server/Email.pm