Remove unused Users#update_uuid endpoint
While working on #18076 I've found that this endpoint could be one of the causes of it. After talking with the team we realized that this endpoint isn't needed anymore as it was superseded with the account merging feature.
#3 Updated by Lucas Di Pentima about 2 months ago
Updates at a47700e6e - branch
Test run: https://ci.arvados.org/job/developer-run-tests/2674/
arvados/v1/users/update_uuidfrom controller & railsAPI.
- Removes it also from Go & R SDKs.
- Updates the documentation, adding an upgrade note about the removal.