CWL: avoid GATK4 pinning with move to latest release
CWL: avoid GATK4 pinning with move to latest release

chapmanb/bcbio-nextgen,a113n/bcbio-nextgen,a113n/bcbio-nextgen,vladsaveliev/bcbio-nextgen,vladsaveliev/bcbio-nextgen,chapmanb/bcbio-nextgen,lbeltrame/bcbio-nextgen,vladsaveliev/bcbio-nextgen,lbeltrame/bcbio-nextgen,a113n/bcbio-nextgen,lbeltrame/bcbio-nextgen,chapmanb/bcbio-nextgen