[DRE-maint] Bug#919805: ruby-mail is "too new" for this

[Thomas Ward]

3.4.6 Redmine doesn't support ruby-mail beyond 2.6.4.  Neither does the
latest 3.4.x release.

This package would need to be updated to Redmine 4.0.1 and track the
4.0.x series to get the proper ruby-mail support.

(Looking into this downstream in Ubuntu, this was discovered.  I am
simply sharing this information for the purposes of making sure this bit
is known here)