Log Message:
Update www/php-piwigo to latest version 10.15.1

We did not update this package for 7 years. The full list of releases
with changes is available here: https://piwigo.org/changelogs

The update is supposed to fix about 60 CVE, although the exact number
is difficult to assess. Some vulnerbilities may have been introduced
in recent releases for which we did not provided a package.

Piwigo 10.15.1 claims to support PHP from version 5 to 8. The upgrade
process works smoothly from previously packaged 2.9.1 version

Approved by pkgsrc freeze warden Jonathan Perkins, and package
maintainer Ryo Onodera.