DbLogController needs some updates on the comments

The DbLogController::overview() method has two @see statements that are not up to date.

@see dblog_clear_log_form()
@see dblog_event()

This functions do not longer exists in Drupal 8 and should be replaced by:

@see Drupal\dblog\Form\DblogClearLogConfirmForm
@see Drupal\dblog\Controller\DbLogController::eventDetails()

Also the DbLogController::topLogMessage has an old comment line:

   *
   * Use one of the above *Report() methods.

That line can be deleted too.