www/baculum-common: Add php 8 support

As per the release notes available in their git repository from here:
https://gitlab.bacula.org/bacula-community-edition/bacula-community/-/blob/Branch-11.0/gui/baculum/ReleaseNotes

this ports supports php 8 from the current version in the tree.

Approved by: portmgr (blanket infrastructure)
Sponsored by: Bounce Experts