Remove experimental Hibernate Search / JGroups integration

The <artifactId>hibernate-search-backend-jgroups</artifactId> has never matured from its experimental status, and should not have been included in WildFly.

We never supported it, it's presence is not documented in EAP docs, and should simply be removed as it was a mistake to include it in the first place.

I'll keep the reference to it as an optional dependency from the module, so that people can still drop in the module if they want to. I just don't believe this should be shipped by default.