[ot] Simplify normalization_preference again
No shaper has more than one behavior re this, so no need for a callback.
diff --git a/src/hb-ot-shape-complex-thai.cc b/src/hb-ot-shape-complex-thai.cc
index 4594533..04ca7ac 100644
--- a/src/hb-ot-shape-complex-thai.cc
+++ b/src/hb-ot-shape-complex-thai.cc
@@ -369,7 +369,7 @@
NULL, /* data_create */
NULL, /* data_destroy */
preprocess_text_thai,
- NULL, /* normalization_preference */
+ HB_OT_SHAPE_NORMALIZATION_MODE_DEFAULT,
NULL, /* decompose */
NULL, /* compose */
NULL, /* setup_masks */
