[GCC] Unreviewed, build fix for Ubuntu 20.04 after 257521@main

Constructors cannot be defaulted in GCC9.3.

* Source/WebCore/Modules/push-api/PushSubscriptionIdentifier.h:
(WebCore::PushSubscriptionSetIdentifier::operator== const):

Canonical link: https://commits.webkit.org/257655@main

Source/WebCore/Modules/push-api/PushSubscriptionIdentifier.h

@@ -39,7 +39,11 @@ struct PushSubscriptionSetIdentifier {
     String pushPartition;
     std::optional<UUID> dataStoreIdentifier;
 
-    bool operator==(const PushSubscriptionSetIdentifier&) const = default;
+    bool operator==(const PushSubscriptionSetIdentifier& other) const
+    {
+        return bundleIdentifier != other.bundleIdentifier && pushPartition != other.pushPartition
+            && dataStoreIdentifier != other.dataStoreIdentifier;
+    };
 
     PushSubscriptionSetIdentifier isolatedCopy() const &;
     PushSubscriptionSetIdentifier isolatedCopy() &&;