adding-new-certificates: Prefer to using "trust anchor" command
    
    There are a couple of methods to install a certificate into the trust
    store: using "trust anchor" or copying the file to
    /etc/pki/ca-trust/source/anchors/.  The former is simpler and more
    flexible as it doesn't require update-ca-trust and the installed
    certificates can be removed with "trust anchor --remove".
    
    For more context, see:
    https://bugzilla.redhat.com/show_bug.cgi?id=2163554
    
    Signed-off-by: Daiki Ueno <dueno@redhat.com>