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
If we go for this `256` field change, then we should make it for *all* files at the same time, so that we could amend JSON configuration as well as output templates at the same time...