cleanup inputdata validation in REST

[belforte]

once Client v3.240520 or later is in production, we can finally ucomment https://github.com/dmwm/CRABServer/blob/886a75271ac769a56ef7eb1bf016d649b3c4ff3a/src/python/CRABInterface/RESTUserWorkflow.py#L363 and cleanup following code

ref: #8372

[belforte]

On HOLD waiting for new client