Add job for PageTriage tests

Created jobs:
browsertests-PageTriage-en.wikipedia.beta.wmflabs.org-linux-chrome-sauce
browsertests-PageTriage-en.wikipedia.beta.wmflabs.org-linux-firefox-sauc
e

Bug: 67134
Change-Id: I5927ce8b94846a4262f4e1b235a13e839936171d