Fix the warning appearing check setup when mail_smtpmode is not confi…

…gured.

Closes #11107

settings/Controller/CheckSetupController.php

@@ -529,7 +529,7 @@ protected function getCronErrors() {
 	}
 
 	protected function isPhpMailerUsed(): bool {
-		return $this->config->getSystemValue('mail_smtpmode', 'php') === 'php';
+		return $this->config->getSystemValue('mail_smtpmode') === 'php';
 	}
 
 	protected function hasOpcacheLoaded(): bool {