message: deleted unused notification key
diff: import User, { UserStatus } from './User';
  -import { BillingInvoice } from './Billing';
  import ChargingStation from './ChargingStation';
  -import Decimal from 'decimal.js';
  import NotificationTask from '../notification/NotificationTask';
  import { SMTPError } from 'emailjs';
  @@ -54,8 +52,7 @@ export type UserNotificationKeys =
  'sendCarCatalogSynchronizationFailed' |
  'sendEndUserErrorNotification' |
  'sendAccountVerificationNotification' |
  - 'sendAdminAccountVerificationNotification' |
  - 'sendUserCreatePassword'
  + 'sendAdminAccountVerificationNotification'
  ;
  export enum UserNotificationType {
  