Bump virtualenv from 20.13.3 to 20.13.4 (#866)

Bumps [virtualenv](https://github.com/pypa/virtualenv) from 20.13.3 to 20.13.4.
- [Release notes](https://github.com/pypa/virtualenv/releases)
- [Changelog](https://github.com/pypa/virtualenv/blob/20.13.4/docs/changelog.rst)
- [Commits](pypa/virtualenv@20.13.3...20.13.4)

---
updated-dependencies:
- dependency-name: virtualenv
  dependency-type: indirect
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>