MAN: Document that it is enough to systemctl restart sssd-kcm.service lately
    
    Related:
    https://pagure.io/SSSD/sssd/issue/3862
    
    We forgot to amend the man page after implementing the sssd-kcm service
    reload.
    
    Reviewed-by: Michal Židek <mzidek@redhat.com>