Revert of [Tracing] Use TracingCategoryObserver in gc statistics

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index d77b7c8f6cc539eda24e135d8cb89d8a456b5c9c..838f52f8032d092f49b1d06afd18638b9e9f9800 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -8087,7 +8087,7 @@
 bool Isolate::GetHeapObjectStatisticsAtLastGC(
     HeapObjectStatistics* object_statistics, size_t type_index) {
   if (!object_statistics) return false;
-  if (V8_LIKELY(!i::FLAG_gc_stats)) return false;
+  if (!i::FLAG_track_gc_object_stats) return false;
 
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);
   i::Heap* heap = isolate->heap();