Rename spack env branch names in our script

The branch names in the repo spack-environments changed to use the format releases/dev-23a and for the spack fork, it was changed to mpsd/v0.19_dev-23a (see spack-environments!36 (merged) we dont worry about that in this script ) This MR updates those changes into our source.

requested review from @hans.fangohr

approved this merge request

Thanks, looks good to me. Please merge when you think the time is right ;-).

merged

mentioned in commit 63f48ebb