Replace VEP option --pick by --per_gene

[maxulysse]

We do have an issue with VEP and the --pick option. It will, for a variant, report only one gene. The behavior we need is instead that only one transcript is reported for each gene. So --pick must likely be replaced with --per_gene. More info here: https://www.ensembl.org/info/docs/tools/vep/script/vep_other.html#pick