The feature flag $wgWBRepoSettings['tmpWbsubscribersSensibleOutput'] was only introduced temporarily to enable a controlled roll-out. Now that the roll-out is finished, we can remove it again.
See the changes associated with the parent task and subtasks for code that was added and now needs to be cleaned up.
A (likely incomplete) list of places to clean up:
- Wikibase.default.php
- ListSubscribers.php
- wmf-config/Wikibase.php
- wmf-config/InitialiseSettings-labs.php:2347