marked create_account.feature with @clean tag, tested on 1.22

As noted in the conventions on
https://www.mediawiki.org/wiki/Manual:Coding_conventions/Cucumber

No other tests in this repo will pass on a clean 1.22 wiki

Change-Id: I30dd3a174b24b4ade8cbefa264a2ce39ce99c41c
Merge "marked create_account.feature with @clean tag, tested on 1.22"