Fix overriding notification subject translation

src/Notifications/ConfirmPayment.php

@@ -60,6 +60,7 @@ public function toMail($notifiable)
         $url = route('cashier.payment', ['id' => $this->paymentId]);
 
         return (new MailMessage)
+            ->subject(__('Confirm Payment'))
             ->greeting(__('Confirm your :amount payment', ['amount' => $this->amount]))
             ->line(__('Extra confirmation is needed to process your payment. Please continue to the payment page by clicking on the button below.'))
             ->action(__('Confirm Payment'), $url);