Remove usages of emails_disabled in favor of emails_enabled for Projects

See merge request !121585



Merged-by: Terri Chu <tchu@gitlab.com>
Approved-by: Terri Chu <tchu@gitlab.com>
Approved-by: Deepika Guliani <dguliani@gitlab.com>
Approved-by: Alex Pooley <apooley@gitlab.com>
Reviewed-by: Joe Snyder <joe.snyder@kitware.com>
Reviewed-by: Nicolas Dular <ndular@gitlab.com>
Reviewed-by: Terri Chu <tchu@gitlab.com>
Reviewed-by: Deepika Guliani <dguliani@gitlab.com>
Co-authored-by: Joseph Snyder <joe.snyder@kitware.com>