Feature flag cleanup: tanuki_bot_indexing
What does this MR do and why?
Removes tanuki_bot_indexing
feature flag which has been active in production and tested.
Rollout issue: https://gitlab.com/gitlab-org/gitlab/-/issues/410682
MR acceptance checklist
This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.
-
I have evaluated the MR acceptance checklist for this MR.
Related to #410682