Since we can now user Parsoid directly (ie $wgVirtualRestConfig['modules']['parsoid']), we can deprecate usage of wgContentTranslationRESTBase.
sx.wmflabs.org is using new setup for example.
Current usages
- ContentTranslation: https://gerrit.wikimedia.org/r/plugins/gitiles/operations/mediawiki-config/+/refs/heads/master/wmf-config/CommonSettings.php#3452