Update documentation to remove token_reviewer_jwt, removed from UI

[NLRemco]

Overview

Removing the usage of token_reviewer_jwt entry from Kubernetes's access UI. Removing from the documentation completely.

Related Issues/Pull Requests

Issue #12951
PR #128

Contributor Checklist

[x] Add relevant docs to upstream Vault repository, or sufficient reasoning why docs won’t be added yet
The docs are altered in this PR
[x] Add output for any tests not ran in CI to the PR description (eg, acceptance tests)
[x] Backwards compatible
Vault keeps working as before, only difference will be approach of the validation of the sent-in JWT token. However, this PR aims towards removing this functionality. This PR however only focusses on UI changes.

[hsimon-hashicorp]

Usually, we err on the side of giving lots of notice when removing functionality, with deprecation notices and announced versions where it will take effect. As such, the Vault engineering teams will be discussing this internally - your patience is appreciated. :)

[NLRemco]

Usually, we err on the side of giving lots of notice when removing functionality, with deprecation notices and announced versions where it will take effect. As such, the Vault engineering teams will be discussing this internally - your patience is appreciated. :)

@hsimon-hashicorp Thank you for the heads up, I'll be looking forward to hearing more!

If taken into consideration and accepted: would it perhaps fit more to first deprecate this feature to then follow up with this PR, especially since this PR is linked with another PR?