Remove left-overs of PushSubscription.curve25519dh

LayoutTests/http/tests/push_messaging/subscribe-encryption-public-key.html

Index: LayoutTests/http/tests/push_messaging/subscribe-encryption-public-key.html
diff --git a/LayoutTests/http/tests/push_messaging/subscribe-encryption-public-key.html b/LayoutTests/http/tests/push_messaging/subscribe-encryption-public-key.html
index 08d60988f2dc0ce4a87b321fddc3a099efe6ab3b..72e98d4edbfd15705103579a41b26ad10438fbb8 100644
--- a/LayoutTests/http/tests/push_messaging/subscribe-encryption-public-key.html
+++ b/LayoutTests/http/tests/push_messaging/subscribe-encryption-public-key.html
@@ -38,9 +38,6 @@
                         return swRegistration.pushManager.subscribe();
                     })
                     .then(function(pushSubscription) {
-                        // TODO(peter): Remove support for the attribute when the embedder has been updated.
-                        assert_idl_attribute(pushSubscription, 'curve25519dh');
-
                         assert_own_property(PushSubscription.prototype, 'getKey');
                         assert_not_equals(pushSubscription.getKey('curve25519dh'), null);
                         assert_equals(pushSubscription.getKey('curve25519dh').byteLength, EXPECTED_KEY_LENGTH);