Remove unused etc/ReqMgrConfig.py

This configuration file is IMO not used anywhere. Only considered in the
scenario in which ReqMgr gets deployed along with WMAgent deploy script,
I don't think we run this anywhere. @sfoulkes, please review.
Merge pull request #4560 from zdenekmaxa/reqmgr-remove-unused-config-file

Remove unused etc/ReqMgrConfig.py