### What
We've had this marked as deprecated through our v4, this PR removes it.
### Worth noting
This updates the deprecation notices with removal notices in the
documentation as well.
### Considerations
The tags API is still located under
/api/admin/features/{featureName}/tags. It should be moved to
/api/admin/projects/{project}/features/{featureName}/tags. I vote we do
that in a separate PR, we'd probably also need to deprecate the existing
tags endpoints for v5 and remove in v6. We could use 308s to signify
that they are moved.
---------
Co-authored-by: Thomas Heartman <thomas@getunleash.ai>
