Drop com.h2database:h2 from Geoserver

 `om.h2database:h2` is brought by Geofence, but it's not used, since Geofence is always configured to use PostGIS.
The `h2-1.1.119.jar` could be removed from the artifacts but we need to check first if the `gt-jdbc-h2-30.3.jar` can also be removed.