[string] Move String.p.toLowerCase to CSA

src/builtins/builtins-intl.cc

Index: src/builtins/builtins-intl.cc
diff --git a/src/builtins/builtins-intl.cc b/src/builtins/builtins-intl.cc
index 1bcdbe7b5aead5f2f81bf6d4b6e704a2e23b478f..c14d73b3b60b69701fad42d74508c5cbfb071c18 100644
--- a/src/builtins/builtins-intl.cc
+++ b/src/builtins/builtins-intl.cc
@@ -16,13 +16,6 @@
 namespace v8 {
 namespace internal {
 
-BUILTIN(StringPrototypeToLowerCaseIntl) {
-  HandleScope scope(isolate);
-  TO_THIS_STRING(string, "String.prototype.toLowerCase");
-  string = String::Flatten(string);
-  return ConvertCase(string, false, isolate);
-}
-
 BUILTIN(StringPrototypeToUpperCaseIntl) {
   HandleScope scope(isolate);
   TO_THIS_STRING(string, "String.prototype.toUpperCase");