FIX: Stop excluding FS minc_modify_header used during fallback registration (#3372)

Author: psadil

docker/files/freesurfer7.3.2-exclude.txt

@@ -795,7 +795,6 @@ freesurfer/mni/bin/minclookup
 freesurfer/mni/bin/mincmakescalar
 freesurfer/mni/bin/mincmakevector
 freesurfer/mni/bin/mincmath
-freesurfer/mni/bin/minc_modify_header
 freesurfer/mni/bin/mincpik
 freesurfer/mni/bin/mincstats
 freesurfer/mni/bin/minctoecat