Change generation of Conda environments to use conda-lock
The latest update of the environment (!1283 (merged)) failed because of a problem using apptainer to install on CVMFS.
Other similar cases (like lb-conda) moved to use conda-lock to build and deploy environments (see https://gitlab.cern.ch/lhcb-core/conda-environments/-/blob/master/.ci/create_environments.sh), so we should do the same here.