Bump virtualenv from 20.26.3 to 20.26.4

Bumps [virtualenv](https://github.com/pypa/virtualenv) from 20.26.3 to 20.26.4.
- [Release notes](https://github.com/pypa/virtualenv/releases)
- [Changelog](https://github.com/pypa/virtualenv/blob/main/docs/changelog.rst)
- [Commits](pypa/virtualenv@20.26.3...20.26.4)

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

Signed-off-by: dependabot[bot] <support@github.com>

requirements.txt

@@ -68,6 +68,6 @@ stack-data==0.6.3
 traitlets==5.14.3
 uritemplate==4.1.1
 urllib3==2.2.2
-virtualenv==20.26.3
+virtualenv==20.26.4
 wcwidth==0.2.13
 whitenoise==6.7.0