configure_system: Simplify UUID generation call in AddUser()

This is a static function so we can just perform an assignment directly.

src/yuzu/configuration/configure_system.cpp

@@ -232,8 +232,7 @@ void ConfigureSystem::SelectUser(const QModelIndex& index) {
 }
 
 void ConfigureSystem::AddUser() {
-    Service::Account::UUID uuid;
+    const auto uuid = Service::Account::UUID::Generate();
-    uuid.Generate();
 
     bool ok = false;
     const auto username =