STYLE: Remove dead code

This is an attempt to retain backwards compatiblity,
on the command line, but this feature was never
properly implemented in ants, and has become
an invalid command line options as of

ANTS commit: bf6aa93e21457c727b0793877d1af3fb5988cebd
Date:   Sat Oct 25 14:15:00 2014 -0500

Author: hjmjohnson

nipype/interfaces/ants/registration.py

@@ -581,13 +581,6 @@ def _formatWinsorizeImageIntensities(self):
         self._quantilesDone = True
         return '--winsorize-image-intensities [ %s, %s ]' % (self.inputs.winsorize_lower_quantile, self.inputs.winsorize_upper_quantile)
 
-    def _formatCollapseLinearTransformsToFixedImageHeader(self):
-        if self.inputs.collapse_linear_transforms_to_fixed_image_header:
-            # return '--collapse-linear-transforms-to-fixed-image-header 1'
-            return ''
-        else:
-            # return '--collapse-linear-transforms-to-fixed-image-header 0'
-            return ''
 
     def _format_arg(self, opt, spec, val):
         if opt == 'fixed_image_mask':
@@ -636,7 +629,7 @@ def _format_arg(self, opt, spec, val):
                 return self._formatWinsorizeImageIntensities()
             return ''  # Must return something for argstr!
         elif opt == 'collapse_linear_transforms_to_fixed_image_header':
-            return self._formatCollapseLinearTransformsToFixedImageHeader()
+            return '' # Command no longer exist, so return empty string for backwards compatibility
         return super(Registration, self)._format_arg(opt, spec, val)
 
     def _outputFileNames(self, prefix, count, transform, inverse=False):