Python Templates: Small fix for gizmo custom geometry

The mouse offset was inverted (the widget was going the opposite direction as the
mouse movement).

release/scripts/templates_py/gizmo_custom_geometry.py

@@ -106,7 +106,7 @@ class MyCustomShapeWidget(Gizmo):
             delta = round(delta)
         if 'PRECISE' in tweak:
             delta /= 10.0
-        value = self.init_value + delta
+        value = self.init_value - delta
         self.target_set_value("offset", value)
         context.area.header_text_set("My Gizmo: %.4f" % value)
         return {'RUNNING_MODAL'}