Update cms-eventdisplay-files.xml

Addressing issues: https://github.com/cernopendata/opendata.cern.ch/issues/311  https://github.com/cernopendata/opendata.cern.ch/issues/154 https://github.com/cernopendata/opendata.cern.ch/issues/333 and https://github.com/cernopendata/opendata.cern.ch/issues/223
> <subfield code="y">Explore and Visualise Events</subfield>

As discussed in #357, we should make this "Explore and visualise events" without caps.