Updated mediawiki/extensions
Project: mediawiki/extensions/MobileFrontend  c2e9638efa1fdf4223f01963909b1843f19ce6a1

Stop npm install downloading phantomjs every time

Declaring this explicitly seems to stop `npm install` downloading
phantomjs every time it is run on my machine which has a different
version of phantomjs installed.

Change-Id: I4dde3ff8891a5965fac790c5a09205bc88febf38