- do not invert height percentage with args.inverted
- this means the absolute height value shown is meaningful now and toggling
  ‘Invert height’ just inverts the mask


git-svn-id: svn://svn.code.sf.net/p/gwyddion/code/trunk/gwyddion@16853 25697fe4-d644-49b8-9d30-be5465f2adf3