Bump the version of virtualenv in tox.ini to pull in the correct version of pip

[codecov[bot]]

Codecov Report

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

Project coverage is 63.92%. Comparing base (e01e32f) to head (9f21e63).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #31 +/- ## ======================================= Coverage 63.92% 63.92% ======================================= Files 11 11 Lines 1009 1009 ======================================= Hits 645 645 Misses 364 364 ``` | [Flag](https://app.codecov.io/gh/fox-it/dissect.evidence/pull/31/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=fox-it) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/fox-it/dissect.evidence/pull/31/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=fox-it) | `63.92% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=fox-it#carryforward-flags-in-the-pull-request-comment) to find out more.

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.