Restore PHP 7.4 support

[codders]

#228 removed support for PHP 7.4. Mediawiki infrastructure still uses PHP 7.4 to run CI jobs for current versions of mediawiki (although mediawiki since 1.42.0 requires PHP 8.1 or later). It would be a kindness to the Mediawiki team to continue to support PHP 7.4 until we have migrated our infrastructure away to a newer version.

[JeroenDeDauw]

Done with #232