Remove C: namespace alias (for categories) from hiwiki config

No objections on hiwiki <https://hi.wikipedia.org/w/index.php?title=विकिपीडिया:प्रबंधक_सूचनापट&oldid=2317744#Requests_for_comment.2FWikimedia_Commons>

Bug: 61431
Change-Id: I62109d645ef15f6e921f868284d2eb908059b873