clustering-test-app: Remove apparently un-used (weird) Tycho dependency

clustering-test-app: Remove apparently un-used (weird) Tycho dependency

I was very surprised to notice something related my old friend Tycho
(who I know well, from a past life..) in c/51447 when glancing over that
change, and wondered what it was used for there, in a particularly
strange fashion... FYI Tycho is, normally, a Maven plugin, used for
among other thing dependency resolution of OSGi bundles from p2
repositories; I've never seen it used as a normal direct dependency, and
can't imagine what it would be good for in normal projects.  So I look
more at this project, and found that Tycho is used for.. nothing at all?
Remove!

Change-Id: I8863406ea5e629e2fbaef207b0cd4357d6875a7a
Signed-off-by: Michael Vorburger <vorburger@redhat.com>