Remove deprecated version of PaymentResponse::ToDictionaryValue.

ios/web/payments/payment_request.cc

Index: ios/web/payments/payment_request.cc
diff --git a/ios/web/payments/payment_request.cc b/ios/web/payments/payment_request.cc
index 788380bd90b39cadfe6b2a169e2954eec11c806d..95b4e9818a88db7141a95384a2e3062204b852bc 100644
--- a/ios/web/payments/payment_request.cc
+++ b/ios/web/payments/payment_request.cc
@@ -334,8 +334,4 @@ std::unique_ptr<base::DictionaryValue> PaymentResponse::ToDictionaryValue()
   return result;
 }
 
-void PaymentResponse::ToDictionaryValue(base::DictionaryValue* value) const {
-  value->MergeDictionary(ToDictionaryValue().get());
-}
-
 }  // namespace web