[Debian-med-packaging] Bug#731921: elastix does not depends on gdcm

[Mathieu Malaterre]

Package: elastix

Please remove explicit B-D on libgdcm2-dev since this is not used. It confuses
dak in thinking there is a reverse dependency.

gdcm is being pulled by the insighttoolkit dependency, which should be
all that is needed.

Thanks