Copy over any opt-out beta preferences so these users still have the legacy conflict workflow after deploying TwoColConflict as the new default.
We skipped this migration for the "small default" release, but it needs to be completed before going default on the remaining wikis.
|beta preference||new preference||behavior|
|no preference||opted-in or no preference yet||default to enabled|
|opted-in||opted-in or no preference yet||enabled; delete beta preference|
|opted-in||opted-out||disabled; delete beta preference|
|opted-out||opted-in or no preference yet||disabled; set new preference to opt-out; delete beta preference|
|opted-out||opted-out||disabled; delete beta preference|
The logic is simple: If a beta opt-out exists, copy that to an opt-out for the new preference, overwriting it. The beta preference is removed to prevent this from happening a second time (for example, after the user opts-in).