Objects are born embedded, so we don't need to check ivpr

It's not necessary to check ivpt because objects are allocated as
"embedded" by default

gc.c

@@ -2734,8 +2734,7 @@ obj_free(rb_objspace_t *objspace, VALUE obj)
 
     switch (BUILTIN_TYPE(obj)) {
       case T_OBJECT:
-        if ((RANY(obj)->as.basic.flags & ROBJECT_EMBED) ||
-            RANY(obj)->as.object.as.heap.ivptr == NULL) {
+        if (RANY(obj)->as.basic.flags & ROBJECT_EMBED) {
             RB_DEBUG_COUNTER_INC(obj_obj_embed);
         }
         else if (ROBJ_TRANSIENT_P(obj)) {