Get rid of weighted average for heap_allocatable_bytes_expand

gcbench on ruby-bench was faring much worse with this enabled. I believe
it increases heap size too much in some cases. Remove for now and re-investigate
later.

Author: luke-gruber

gc/default/default.c

@@ -7126,13 +7126,13 @@ gc_marks_finish(rb_objspace_t *objspace)
 
             if (full_marking) {
                 /* Use weighted average slot size since total_slots spans all heaps */
-                size_t total_heap_bytes = 0;
-                for (int i = 0; i < HEAP_COUNT; i++) {
-                    total_heap_bytes += heaps[i].total_slots * heaps[i].slot_size;
-                }
-                size_t avg_slot_size = total_slots > 0 ? total_heap_bytes / total_slots : (size_t)heaps[0].slot_size;
-                heap_allocatable_bytes_expand(objspace, NULL, sweep_slots, total_slots, avg_slot_size);
-                //heap_allocatable_bytes_expand(objspace, NULL, sweep_slots, total_slots, heaps[0].slot_size);
+                /*size_t total_heap_bytes = 0;*/
+                /*for (int i = 0; i < HEAP_COUNT; i++) {*/
+                    /*total_heap_bytes += heaps[i].total_slots * heaps[i].slot_size;*/
+                /*}*/
+                /*size_t avg_slot_size = total_slots > 0 ? total_heap_bytes / total_slots : (size_t)heaps[0].slot_size;*/
+                /*heap_allocatable_bytes_expand(objspace, NULL, sweep_slots, total_slots, avg_slot_size);*/
+                heap_allocatable_bytes_expand(objspace, NULL, sweep_slots, total_slots, heaps[0].slot_size);
             }
         }