appstore-build-publish.yml breaks with 29-only apps due to missing latest-29.zip and master having dropped "php-min"

[nickvergessen]

• Ref chore(release): Fix build action while there is no latest-29 package spreed#12070

[blizzz]

In the fallback, we could try to parse https://github.com/nextcloud-releases/updater_server/blob/master/config/config.php and find the compatible version based on the php min version.