build(deps): bump virtualenv from 20.13.3 to 20.13.4

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: direct:production
  update-type: version-update:semver-patch
...

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

requirements.txt

@@ -40,5 +40,5 @@ toml==0.10.2
 typed-ast==1.5.2
 typing-extensions==4.1.1
 urllib3==1.26.9
-virtualenv==20.13.3
+virtualenv==20.13.4
 wrapt==1.14.0