Remove page.QueryPage

QueryPage is not implemented in Wikibase yet, there are no uses of
a stub class in pywikibot, and there is no novel code in this stub
that warrants keeping while we wait for the functionality to exist
in the Wikibase software.

Change-Id: I9bcdb022c7e7e4db2d24327a29531e417c16ce76
Merge "Remove page.QueryPage"