operations: Always use structured errors in UserCreateTag RPC
With 0fedeb41 (operations: Introduce structured errors for UserCreateTag, 2022-07-22) we have adapted the UserCreateTag RPC to return structured errors instead of embedding errors in a successful response. This both improves visibility into this RPC and fixes cases where we needlessly create replication jobs due to missing votes.
This code has been rolled out to production on August 3rd without any observed negative fallout. Remove the feature flag guarding it.
Changelog: changed
Closes #4372 (closed)