Bump retry count on some flaky tests
    
    The silverblue tests are flaky because of
    https://github.com/fedora-silverblue/issue-tracker/issues/548 .
    The desktop_upgrade_encrypted test is flaky on Rawhide (so, when
    booting from F40 initially) since we switched to UEFI, not sure
    if it's because of UEFI somehow or just a timing coincidence.
    Am going to look into it, but for now this should save lots of
    manual restarting.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>