REF: download_data: added PAM50
REF: download_data: added PAM50

Former-commit-id: 923e9b624b73a1bff4ec078c3965da22b43865f2
Former-commit-id: 59f318879a1452a8831db70c643ed87ab1d8cdf0
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox