scripts/sct_download_data.py: update sct_testing_data links
scripts/sct_download_data.py: update sct_testing_data links


Former-commit-id: af68b627e570fe3791be6873bea2d2211453fd92
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox