remove need for a targetplatforms/jbosstoolstarget/neon site

For the last few years, we've had an associate site ref inside the JBT agg site, pointing at "the latest maximum TP", eg., http://download.jboss.org/jbosstools/targetplatforms/jbosstoolstarget/mars/

But since we now always co-release JBT with its TP in the same URL, this is only useful for someone who wants to do an OFFLINE install using the zip, which will then go ONLINE to resolve TP dependencies. It's at best a broken use case, and at worst it's unnecessary cruft to maintain.

Therefore I propose we stop linking to this site.

We can build the aggregates using a specific TP (the one in the parent pom, natch), and simply NOT use an associate site in the JBT aggregate site build.