Finish cleanup work for VOL-4308

Stale/unused repositories marked as deprecated during the voltha-2.9 release with a comment that final removal would occur at the end of 2022.

Work on final removal:

Currently some repos are outdated, old and stale. Let's put a banner on the README with deprecation not and block merges in gerrit. They will be removed at the end of the 2022 2.8 LTS release.
Openonu-py (https://gerrit.opencord.org/admin/repos/voltha-openonu-adapter)
Ofagent-py
Voltha (python version)
Pyvoltha
Voltha-bbsim
Omci-sim
Kind-voltha
https://github.com/opencord/ponsim – directly delete – is empt.
https://github.com/opencord/voltha-ponsimonu-adapter
https://github.com/opencord/voltha-ponsimolt-adapter
https://github.com/opencord/voltha-simonu-adapter
https://github.com/opencord/voltha-simolt-adapter
https://github.com/opencord/abstract-olt
https://gerrit.opencord.org/admin/repos/voltha-python-base