Bump virtualenv from 20.25.0 to 20.26.6

Bumps [virtualenv](https://github.com/pypa/virtualenv) from 20.25.0 to 20.26.6.
- [Release notes](https://github.com/pypa/virtualenv/releases)
- [Changelog](https://github.com/pypa/virtualenv/blob/main/docs/changelog.rst)
- [Commits](pypa/virtualenv@20.25.0...20.26.6)

---
updated-dependencies:
- dependency-name: virtualenv
  dependency-type: direct:development
...

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

requirements-dev.txt

@@ -168,7 +168,7 @@ tzdata==2023.4
     # via pandas
 uvicorn==0.27.0.post1
     # via datahub (pyproject.toml)
-virtualenv==20.25.0
+virtualenv==20.26.6
     # via pre-commit
 wheel==0.42.0
     # via pip-tools