MAN: The timeout option doesn't say after how many heartbeats will the process be killed
    
    Text added in timeout section of sssd.conf man page describing number of heartbeat missed before process self kills itself.
    
    Resolves: https://pagure.io/SSSD/sssd/issue/3398
    
    Reviewed-by: Fabiano Fidêncio <fidencio@redhat.com>