Updated mediawiki/extensions
Project: mediawiki/extensions/EtherpadLite  af4adc388d100de0e0691118fd86875f9563d90b

Follow-up I7d4bb9062. Register tracking category used.

This allows etherpadlite-tracking-category to appear in the newly added
[[Special:TrackingCategories]].

Bug: 63284
Change-Id: Id7151d76807b12f2e330d123bd7b5678b07d9b64