change deprecated hzdr repo URL to codebase URL

The hereon NetCDF binding rules come back into focus.

Starting a review at the README I recognised the old hzdr URL is in use here (There might be more URLs to be changed in the whole documentation).

Even if there is a redirection of the URL, the URL should correspond to the current real path in order to be consistent.

Old: https://gitlab.hzdr.de/hcdc/hereon-netcdf/hereon-netcdf-en New: https://codebase.helmholtz.cloud/hcdc/hereon-netcdf/hereon-netcdf-en

Do you agree @Chilipp? If so, I open up a branch where I correct for general consistency.