message: API: Fix two NotificationController doc typos
diff: @@ -64,7 +64,7 @@ export class NotificationController {
  *
  * @apiError NotFoundError Did not find the targetId of targetType.
  * @apiError BadRequestError Invalid targetType.
  - * @apiError ForbiddenError The teacher doen't have access to the corresponding course.
  + * @apiError ForbiddenError The teacher doesn't have access to the corresponding course.
  * @apiError InternalServerError No course was found for a given existing lecture.
  * @apiError InternalServerError No course was found for a given existing unit.
  */
  @@ -103,7 +103,7 @@ export class NotificationController {
  *
  * @apiError NotFoundError Did not find the targetId of targetType.
  * @apiError BadRequestError Invalid targetType.
  - * @apiError ForbiddenError The teacher doen't have access to the corresponding course (if targetType isn't 'text'-only).
  + * @apiError ForbiddenError The teacher doesn't have access to the corresponding course (if targetType isn't 'text'-only).
  * @apiError InternalServerError No course was found for a given existing lecture.
  * @apiError InternalServerError No course was found for a given existing unit.
  */
  