dwi2tensor: Fixing up order of references block
dwi2tensor: Fixing up order of references block

* This needs to immediately precedes the arguments block or else the crawler used to fetch references to present on the website will ignore the reference

MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3