qunit.completenessTest: Ignore mw.loader.moduleRegistry

qunit.completenessTest: Ignore mw.loader.moduleRegistry

It was iterating over it and considering its 'script' properties
to be methods that had to be tested.

The CompletnessTest before this change is filled with stuff like:
- loader.moduleRegistry.skins.vector.js.script
- loader.moduleRegistry.mediawiki.api.script
- loader.moduleRegistry.mediawiki.Title.script
- ..

And was actually causing it to hit hard limit and thus actual
lots of actual methods were no longer inspected by the test.

Change-Id: I13fbf1224b48aa34a7bb01fdc0543023e502bb4f