Revert of [turbofan] Add support for copy-on-write element stores.

src/compiler/js-graph.cc

Index: src/compiler/js-graph.cc
diff --git a/src/compiler/js-graph.cc b/src/compiler/js-graph.cc
index d8a8af412a9cbcad453d91a21c0648473809d557..ea3ec5e6dd1ed4be43a2961a4f9b23c9d1dff96f 100644
--- a/src/compiler/js-graph.cc
+++ b/src/compiler/js-graph.cc
@@ -50,11 +50,6 @@
 
 Node* JSGraph::EmptyStringConstant() {
   return CACHED(kEmptyStringConstant, HeapConstant(factory()->empty_string()));
-}
-
-Node* JSGraph::FixedArrayMapConstant() {
-  return CACHED(kFixedArrayMapConstant,
-                HeapConstant(factory()->fixed_array_map()));
 }
 
 Node* JSGraph::HeapNumberMapConstant() {