[OT] Simplify fallback positioning condition

src/hb-ot-shape-fallback.cc

@@ -348,8 +348,7 @@ position_cluster (const hb_ot_shape_plan_t *plan,
 
   /* Find the base glyph */
   for (unsigned int i = start; i < end; i++)
-    if (is_a_ligature (buffer->info[i]) ||
-        !HB_UNICODE_GENERAL_CATEGORY_IS_MARK (_hb_glyph_info_get_general_category (&buffer->info[i])))
+    if (!HB_UNICODE_GENERAL_CATEGORY_IS_MARK (_hb_glyph_info_get_general_category (&buffer->info[i])))
     {
       position_around_base (plan, font, buffer, i, end);
       break;