Fix VE browser tests to switch to VE from source editor

This essentially reverts 744873c. VE is the default only in
mediawiki-vagrant (until If6f5ec21461dbc8ca0cfbe879ba27bc650e7175b is
merged), on beta labs, and many wikis (enwiki included) it's an opt-in
beta feature so mobile will load a wikitext editor by default.

Change-Id: I3bf456747e5cd51d69b0dccd51bba05230d114e8
Merge "Fix VE browser tests to switch to VE from source editor"