remove CMIP6_DataRequest_CF_issues?

[taylor13]

Given that Martin maintains https://github.com/cmip6dr , Is this still needed? Probably not, so let's remove it.

[durack1]

@taylor13 there seems to have been no activity in this repo for quite sometime so I agree we should delete it - I'll await confirmation from @martinjuckes before doing this however

[durack1]

@taylor13 I have heard nothing from @martinjuckes so I assume it's fine to purge this repo

[durack1]

@martinjuckes it seems this repo is no longer in use, I'm doing some cleaning up, so am wondering if I can purge this?

[durack1]

@zklaus this is another candidate for deletion