change embedded links from cloud.helmholtz.de to helmholtz.cloud
This changes all embedded links from (still working but deprecated) cloud.helmholtz.de to helmholtz.cloud.
Since all links are embedded, this does not influence the appearance/formatting.
Once approved & merged, @jandt-desy will upload the results to hifis.net
Edited by Uwe Jandt (DESY, HIFIS)