The scripts generating CheCluster refernce`checluster-properties.adoc`, and Che server properties reference`system-variables.adoc`, can only generate the output for the released versions.

For the che-docs main branch (doc /next/), we should rather generate these from the upstream `main` branch.

Expected implementation: if the script doesn't find a release (ex: 7.54.x), it falls back using the `main` branch, rather than failing.