REF: comment unused methods to compute CSA. Fix #971
REF: comment unused methods to compute CSA. Fix #971

Former-commit-id: 4d9e181b91be95d4b71cde83b95a20666d108a2a
Former-commit-id: 3cb9d1347316d38dd44b6c191cef27ecda16a899
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox