Fix return code of AppConfig::deleteUserValue

Signed-off-by: Morris Jobke <hey@morrisjobke.de>

lib/private/AppFramework/Services/AppConfig.php

@@ -70,6 +70,6 @@ class AppConfig implements IAppConfig {
 	}
 
 	public function deleteUserValue(string $userId, string $key): void {
-		return $this->config->deleteUserValue($userId, $this->appName, $key);
+		$this->config->deleteUserValue($userId, $this->appName, $key);
 	}
 }