Fix distortion_parameters indentation

It was wrong, but it is now working properly.

Signed-off-by: Patrick Avery <patrick.avery@kitware.com>

hexrd/ui/resources/calibration/structureless_params_tree_view.yml

@@ -21,7 +21,7 @@ detectors:
         Y: '{det}_tvec_y'
         Z: '{det}_tvec_z'
     radius: '{det}_radius'
-  distortion parameters:
+    distortion parameters:
 Debye-Scherrer ring means:
 engineering constraints:
   distance between plates: tardis_distance_between_plates