[tests] Skip test_pages_with_property_generator test for wikia
[tests] Skip test_pages_with_property_generator test for wikia

wikia has mw version 1.19 but 1.21+ is needed for Propery generator.
Skip this test for wikia.

Bug: T214009
Change-Id: I3cef33a0b11a170c700b187aa791a5cbd411cf98

wikimedia/pywikibot-core,PersianWikipedia/pywikibot-core,wikimedia/pywikibot-core