Remove PromptSkimming from the system

The ProdAgent is retired, this workflow is not valid anymore.
The OpenRunningRequests provide support for PromptSkim without an
actual relation to the T0 and iyt is also included in the PromptReco
spec.

This is part of the effor to improve the argument validation.
Remove the RelVal MC Spec

It was unmaintained and unused. Its purpose is fully
contained in the TaskChain spec (i.e. RelVals), so it's better
to cleanup now that the spec revamp is happening.

This is part of the effort to improve the argument validation.
Merge pull request #4688 from dballesteros7/removePromptSkim

Remove PromptSkimming from the system
Merge pull request #4687 from dballesteros7/removeRelValMC

Remove the RelVal MC Spec