Fix typehint for ResetPassword::toMailUsing() (#50163)

Author: KKSzymanowski

src/Illuminate/Auth/Notifications/ResetPassword.php

@@ -25,7 +25,7 @@ class ResetPassword extends Notification
     /**
      * The callback that should be used to build the mail message.
      *
-     * @var (\Closure(mixed, string): \Illuminate\Notifications\Messages\MailMessage)|null
+     * @var (\Closure(mixed, string): \Illuminate\Notifications\Messages\MailMessage|\Illuminate\Contracts\Mail\Mailable)|null
      */
     public static $toMailCallback;
 
@@ -114,7 +114,7 @@ public static function createUrlUsing($callback)
     /**
      * Set a callback that should be used when building the notification mail message.
      *
-     * @param  \Closure(mixed, string): \Illuminate\Notifications\Messages\MailMessage  $callback
+     * @param  \Closure(mixed, string): (\Illuminate\Notifications\Messages\MailMessage|\Illuminate\Contracts\Mail\Mailable)  $callback
      * @return void
      */
     public static function toMailUsing($callback)