Rename the address type since it will likely be used for other purposes.

We will most likely want to use the same type in other places. For
example, billing address with a card payment.

specs/paymentrequest.html

@@ -234,7 +234,7 @@ <h2>PaymentRequest interface</h2>
           Promise&lt;PaymentResponse&gt; show();
           void abort();
 
-          readonly attribute ShippingAddress? shippingAddress;
+          readonly attribute PaymentAddress? shippingAddress;
           readonly attribute DOMString? shippingOption;
 
           /* Supports "shippingaddresschange" event */
@@ -766,9 +766,9 @@ <h2>PaymentItem dictionary</h2>
     </section>
 
     <section>
-      <h2>ShippingAddress interface</h2>
+      <h2>PaymentAddress interface</h2>
       <pre class="idl">
-        interface ShippingAddress {
+        interface PaymentAddress {
           readonly attribute DOMString regionCode;
           readonly attribute FrozenArray&lt;DOMString&gt; addressLine;
           readonly attribute DOMString administrativeArea;
@@ -863,7 +863,7 @@ <h2>PaymentResponse interface</h2>
         interface PaymentResponse {
           readonly attribute DOMString methodName;
           readonly attribute object details;
-          readonly attribute ShippingAddress? shippingAddress;
+          readonly attribute PaymentAddress? shippingAddress;
           readonly attribute DOMString? payerEmail;
           readonly attribute DOMString? payerPhone;