[doc] Stop indexing third_party documents in Hugo
[doc] Stop indexing third_party documents in Hugo

Signed-off-by: Miguel Osorio <c7c97b215f812c2e8a32efd57ad5e976a6eb9e45@google.com>

lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan