If applying morx, apply kern table even if GPOS is present and has kern

Since we won't be applying GPOS if morx...

To be adjusted as I receive more information from Ned.  But for now
fixes this:

$ ./hb-shape GillSans.ttc Ty
[T=0+1109|y=1@-128,0+769]

Fixes https://github.com/harfbuzz/harfbuzz/issues/1982 for now.

src/hb-ot-shape.cc

@@ -166,7 +166,7 @@ hb_ot_shape_planner_t::compile (hb_ot_shape_plan_t           &plan,
     plan.apply_kerx = true;
 #endif
 
-  if (!plan.apply_kerx && !has_gpos_kern)
+  if (!plan.apply_kerx && (!has_gpos_kern || !plan.apply_gpos))
   {
     /* Apparently Apple applies kerx if GPOS kern was not applied. */
 #ifndef HB_NO_AAT_SHAPE