We had daily selenium jobs targetting beta and using the mediawiki-selenium rubygem. That has been deprecated for two years.
Those jobs were still running on legacy Jessie WMCS instances:
Using the label BrowserTests.
It is all legacy and should be removed.
https://gerrit.wikimedia.org/r/556252 removed the last two jobs: selenium-MinervaNeue and selenium-QuickSurveys