featureflag: Unconditionally enable transactional removal of repos

With a22bb54c (coordinator: Fix repo creation/removal race for up-to-date secondaries, 2021-07-07), we have introduced a feature flag which enables transactions for the RemoveRepository() RPC. This was required in order to plug a race when we get both a RemoveRepository() and CreateRepository() RPC in quick succession, where the scheduled replication job of the former RPC might kick in while we are about to create the repository. By doing transactional voting, we avoid creating a replication job for the deletion as long as the secondaries are up-to-date.

This feature flag has been introduced in v14.1, but has been backported to v14.0. Given its heightened exposure and the fact that it's been enabled in production for some time now without any issue, this commit removes the feature flag altogether while skipping the default-enabled step.

Changelog: fixed

Closes #3699 (closed)