Updated Ruby gems

mediawiki_selenium 0.2.23 should fix “No such file or directory”[1]
error message.

1:
https://integration.wikimedia.org/ci/view/BrowserTests/job/browsertests-
Flow-test2.wikipedia.org-linux-firefox/6/consoleFull

Change-Id: I1b62118d4605b5e7d50768ed76a3b084023e4754