mail/rubygem-mail: Revert "mail/rubygem-mail: Fix dependency with Ruby 3.1"

This reverts commit c22b848a5d76a963762a9ea244c029c3d485d693.

After the commit build of the port fails with patch error because
version of devel/ruby-gems in 2022Q1 branch (3.0.8) is different from
that of main branch (3.3.7). Moreover version 3.0.8 isn't compatible
with Ruby 3.x and it is pointless to fix dependency with Ruby 3.1.
So fix the build error by reverting it.

Reported by: Cedric Berger (via private mail)
Approved by: fluffy (ports-secteam)