www/webtrees21: Update to 2.1.22

Introduce PHP flavors. This branch is targeted to PHP 7.4-8.2 so should
use IGNORE_WITH_PHP.
Conflicts webtree20 so doesn't need change DOCSDIR and WWWDIR
from default and can remove SUB_LIST variable.
Move LICENSE.md from PORTDOCS to LICENSE_FILE.
Switch to DISTVERSION.

Changelog: https://webtrees.net/blog/2024/11/30/new-webtrees-release-2-2-1.html

PR: 283149
Approved by: submitter is maintainer