Fixed shape_predictor_trainer padding so that it behaves as it used to. In

dlib 19.7 the padding code was changed and accidentally doubled the size of the
applied padding when in the older (and still default) landmark_relative padding
mode.  It's not a huge deal either way, but this change reverts back to the
intended behavior.

dlib/image_processing/shape_predictor_trainer.h

@@ -744,10 +744,10 @@ namespace dlib
             // Figure out the bounds on the object shapes.  We will sample uniformly
             // from this box.
             matrix<float> temp = reshape(initial_shape, initial_shape.size()/2, 2);
-            double min_x = min(colm(temp,0))-padding;
-            double min_y = min(colm(temp,1))-padding;
-            double max_x = max(colm(temp,0))+padding;
-            double max_y = max(colm(temp,1))+padding;
+            double min_x = min(colm(temp,0));
+            double min_y = min(colm(temp,1));
+            double max_x = max(colm(temp,0));
+            double max_y = max(colm(temp,1));
 
             if (get_padding_mode() == bounding_box_relative)
             {