[Fix] Nextflow usage info

[St3451]

Issue

Nextflow usage information suggests to load nextflow using the IRB cluster module loader asmodule load nextflow, however:

1. this command fails, the correct one seems to be module load Nextflow/22.10.7
2. the above command will load an old version of the software. An alternative and potentially better working solution could be to create a conda env and install an up to date version using conda create -n nextflow -c conda-forge -c bioconda nextflow -y