WIP Update cms-external-resources.xml

Trying to address https://github.com/cernopendata/opendata.cern.ch/pull/493#issuecomment-60944042
Will fix the link to the dataset
The point is that the record has two 980s, which will make it to appear in two collections, under "CMS External Resources" and under "CMS Open Data Instructions", as if it were a dupe...