Fix: GPv3: Newly added objects don't have the Use Lights setting set

The issue was that the code checked for the `OB_GPENCIL_LEGACY`
type instead of `OB_GREASE_PENCIL`.

source/blender/blenkernel/intern/object.cc

@@ -1996,7 +1996,7 @@ static void object_init(Object *ob, const short ob_type)
     ob->upflag = OB_POSY;
   }
 
-  if (ob->type == OB_GPENCIL_LEGACY) {
+  if (ob->type == OB_GREASE_PENCIL) {
     ob->dtx |= OB_USE_GPENCIL_LIGHTS;
   }