Changes

gbproxy: update ttcn3 configuration to reflect osmo-gbproxy.cfg

In Change-Id I80de01c96185c60fe2de7a8ffa9daed2669658e1 we updated
only the osmo-gbproxy.cfg, but noth the GBProxy_Tests.cfg for the
test suite, which of course won't work.

Change-Id: I35603dc76926d76e57993f7eab1354eea8d25dad
Related: SYS#5226