build(deps): bump virtualenv from 20.15.0 to 20.15.1

Bumps [virtualenv](https://github.com/pypa/virtualenv) from 20.15.0 to 20.15.1.
- [Release notes](https://github.com/pypa/virtualenv/releases)
- [Changelog](https://github.com/pypa/virtualenv/blob/20.15.1/docs/changelog.rst)
- [Commits](pypa/virtualenv@20.15.0...20.15.1)

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

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

requirements-ci.txt

@@ -2,5 +2,5 @@ pip==22.1.2
 requirements-builder==0.4.4
 setuptools==59.6.0; python_version < '3.7'
 setuptools==62.6.0; python_version >= '3.7'
-virtualenv==20.15.0
+virtualenv==20.15.1
 wheel==0.37.1