Bump virtualenv from 20.4.2 to 20.4.3

Bumps [virtualenv](https://github.com/pypa/virtualenv) from 20.4.2 to 20.4.3.
- [Release notes](https://github.com/pypa/virtualenv/releases)
- [Changelog](https://github.com/pypa/virtualenv/blob/main/docs/changelog.rst)
- [Commits](pypa/virtualenv@20.4.2...20.4.3)

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