Retire PaymentDetailsModifierData flag

Web payments modifiers shipped in M62
https://chromium-review.googlesource.com/632597
https://www.chromestatus.com/feature/6636936064139264

BUG=660926

Change-Id: Id0ab64582180f3cba875618efe3b31177d9ce9b8
Reviewed-on: https://chromium-review.googlesource.com/1164973Reviewed-by: Rouslan Solomakhin <rouslan@chromium.org>
Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
Commit-Queue: Eric Willigers <ericwilligers@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581380}

third_party/blink/renderer/modules/payments/payment_details_modifier.idl

@@ -8,5 +8,5 @@ dictionary PaymentDetailsModifier {
     [ImplementedAs=supportedMethod] required DOMString supportedMethods;
     PaymentItem total;
     sequence<PaymentItem> additionalDisplayItems;
-    [RuntimeEnabled=PaymentDetailsModifierData] object data;
+    object data;
 };

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -946,10 +946,6 @@
       name: "PaymentApp",
       status: "experimental",
     },
-    {
-      name: "PaymentDetailsModifierData",
-      status: "stable",
-    },
     // PaymentRequest is enabled by default on Android
     {
       name: "PaymentRequest",