bench aead: Do Cartesian product, not zip

[aochagavia]

It looks like this was missed by 6cda863

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (464d367) 96.01% compared to head (37c8c03) 96.01%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1836 +/- ## ======================================= Coverage 96.01% 96.01% ======================================= Files 136 136 Lines 20687 20687 Branches 226 226 ======================================= Hits 19863 19863 Misses 791 791 Partials 33 33 ```

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[briansmith]

Thank you!