Revert "ENH: Re-enable spm.Realign to take lists of lists of files"

This reverts commit da966f9.

Author: effigies

nipype/interfaces/spm/preprocess.py

@@ -125,7 +125,7 @@ def _list_outputs(self):
 
 class RealignInputSpec(SPMCommandInputSpec):
     in_files = InputMultiPath(
-        InputMultiPath(ImageFileSPM(exists=True)),
+        ImageFileSPM(exists=True),
         field='data',
         mandatory=True,
         copyfile=True,