databases/pspg: Update pkg-message: Improved the alias suggestion

PR: 223805
Submitted by: Dmitri Goutnik <dg@syrec.org>
Reported by: Christoph Moench-Tegeder <cmt@burggraben.net>
Approved by: tcberner (mentor)
Differential Revision: https://reviews.freebsd.org/D13195