mail/getmail6: Update to version 6.14

https://github.com/getmail6/getmail6/releases/tag/v6.13
https://github.com/getmail6/getmail6/releases/tag/v6.14

While here, remove conflict with mail/getmail, which was removed from the
ports tree.

PR: 252672
Submitted by: Michael Bueker <m.bueker@berlin.de> (maintainer)