REF: remove flag -a (already in -param). Fix #637
REF: remove flag -a (already in -param). Fix #637

Former-commit-id: 00c3a53e08930e63ef87722e743bb221a9c9eefc
Former-commit-id: 01bf6d48ebd36030a58011d357ed96145dbb4702
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox