2b3b41d man/sss_ssh_knownhostsproxy: fix typo pubkeys -> pubkey

Authored and Committed by fidencio 5 years ago
    man/sss_ssh_knownhostsproxy: fix typo pubkeys -> pubkey
    
    In commit 36f2fe8f63 a discrepancy between the command line option and
    the manpage has been introduced.
    
    Related:
    https://pagure.io/SSSD/sssd/issue/3542
    
    Signed-off-by: Fabiano FidĂȘncio <fidencio@redhat.com>
    Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>