IRS is live on ptwiki and should remain so until it can be successfully transitioned to the the new workflow. Other wikis will start out on v2 and shouldn't be impacted by this.
Acceptance criteria:
- [x] flag exists to enable legacy version on ptwiki ([Add a configuration option to use v1 or v2 non-emergency IRS flow](https://gerrit.wikimedia.org/r/c/mediawiki/extensions/ReportIncident/+/1207839))
- [x] IRS can handle 2 flag-dependent pathways ([Stub out v2 non-emergency workflow submit success page](https://gerrit.wikimedia.org/r/c/mediawiki/extensions/ReportIncident/+/1206874))
- [] config is deployed to support this ([Enable IRS v2 non-emergency workflow on beta](https://gerrit.wikimedia.org/r/c/operations/mediawiki-config/+/1216561), [Revert^2 "Enable v2 non-emergency workflow by default"](https://gerrit.wikimedia.org/r/c/operations/mediawiki-config/+/1219533))