Removing dependancy on SpecialDisambiguations since it's being axed.

This is a quick hack to make sure Special:PagesWithoutScans doesn't
break when https://gerrit.wikimedia.org/r/#/c/74096/ is merged. The
underlying logic of how it finds disambiguation pages should be
updated at some point to use the new 'disambiguations' property.

Bug: 35981
Change-Id: I41637ea43a9e5000bcb8a782441ce36f1068881f
Merge "Removing dependancy on SpecialDisambiguations since it's being axed."