Sync gen-vowel-constraints.py with current output

src/gen-vowel-constraints.py

@@ -180,6 +180,9 @@ print ('_hb_preprocess_text_vowel_constraints (const hb_ot_shape_plan_t *plan HB
 print ('\t\t\t\t       hb_buffer_t              *buffer,')
 print ('\t\t\t\t       hb_font_t                *font HB_UNUSED)')
 print ('{')
+print ('#if defined(HB_NO_OT_SHAPE_COMPLEX_VOWEL_CONSTRAINTS)')
+print ('  return;')
+print ('#endif')
 print ('  if (buffer->flags & HB_BUFFER_FLAG_DO_NOT_INSERT_DOTTED_CIRCLE)')
 print ('    return;')
 print ()