Make mwext-WikibaseQuery-testextensions-master non-voting

There's a few test failures that are known but shouldn't block
merges meanwhile (per JeroenDeDauw).

https://integration.wikimedia.org/ci/job/mwext-WikibaseQuery-testextensions-master/16/console

Change-Id: I4c5ef9f3df1d88a8115ce41f86f5a4dd32f93951