* Use HTTPS for sk89q maven repo
Newer Maven releases don't allow use of http endpoints. Bump this to the secure https endpoint.
* Migrate sk89q maven repo to enginehub
Both URLs point to the same place, but according to https://worldguard.enginehub.org/en/latest/developer/dependency/ enginehub is the preferred source.
* Bump Java to Adoptium Hotspot JDK 11