Remove the global Strength enum class completely.

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index ddca0d616be838700b73a45c09f73480d3caaccf..fe7802cc8784e9921fd8ee2611dc7d55d3b67998 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -4538,16 +4538,6 @@ bool Map::is_migration_target() {
 }
 
 
-void Map::set_is_strong() {
-  set_bit_field3(IsStrong::update(bit_field3(), true));
-}
-
-
-bool Map::is_strong() {
-  return IsStrong::decode(bit_field3());
-}
-
-
 void Map::set_new_target_is_base(bool value) {
   set_bit_field3(NewTargetIsBase::update(bit_field3(), value));
 }