rm. ref to 'MEDIAWIKI_DB_INSTANCE' in favour of cohort meta instance from settings.
rm. ref to 'MEDIAWIKI_DB_INSTANCE' in favour of cohort meta instance from settings.

rfaulkner/wikipedia_user_metrics,wikimedia/analytics-user-metrics,wikimedia/user_metrics,wikimedia/analytics-user-metrics,rfaulkner/wikipedia_user_metrics,rfaulkner/wikipedia_user_metrics,wikimedia/analytics-user-metrics,wikimedia/user_metrics,wikimedia/user_metrics