PaymentHandler: Implement PaymentInstruments.delete().

components/payments/mojom/payment_app.mojom

Index: components/payments/mojom/payment_app.mojom
diff --git a/components/payments/mojom/payment_app.mojom b/components/payments/mojom/payment_app.mojom
index 5cc4e3bca4ea82398d46887aada18e412b7d4cb5..ccda4c7df095eb0562b9794848ccf7a59b457097 100644
--- a/components/payments/mojom/payment_app.mojom
+++ b/components/payments/mojom/payment_app.mojom
@@ -48,9 +48,11 @@ interface PaymentManager {
       => (PaymentAppManifestError error);
   GetManifest()
       => (PaymentAppManifest payment_app_manifest, PaymentAppManifestError error);
-  SetPaymentInstrument(string instrumentKey, PaymentInstrument instrument)
+  DeletePaymentInstrument(string instrument_key)
       => (PaymentHandlerStatus status);
-  GetPaymentInstrument(string instrumentKey)
+  SetPaymentInstrument(string instrument_key, PaymentInstrument instrument)
+      => (PaymentHandlerStatus status);
+  GetPaymentInstrument(string instrument_key)
       => (PaymentInstrument instrument, PaymentHandlerStatus status);
 };