Corrected skip_until_first_slice in ground_truth.
Corrected skip_until_first_slice in ground_truth.


Former-commit-id: 4a15b370960be906607788a35b4f9afc37ef59ee
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox