test/py: efi_secboot: Remove unnecessary cert-to-efi-hash-list option

'cert-to-efi-hash-list -t 0' does not work as expected, it produces
indeterminate timestamp.

  $ cert-to-efi-hash-list -t 0 -s 256 db.crt dbx_hash.crl
  TimeOfRevocation is 0-113-0 00:00:255

If we need the CRL revoked for all the time, just don't specify
'-t' option.

  $ cert-to-efi-hash-list -s 256 db.crt dbx_hash.crl
  TimeOfRevocation is 0-0-0 00:00:00

Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>