Fix the Qunit tests

This is done by removing the wikibase.formatters.QuantityFormatter.tests
test module as the associated module has been removed with Ic28d1cb.
Furthermore the dependency on mediawiki.tests.qunit.testrunner has been
fixed (that module has been made a test only one in core with I21e69f5)

Change-Id: I4dbc078aff926748489a13d4a9e76f0991fce89c