Bump virtualenv from 16.0.0 to 16.6.0
Bump virtualenv from 16.0.0 to 16.6.0

Bumps [virtualenv](https://github.com/pypa/virtualenv) from 16.0.0 to 16.6.0.
- [Release notes](https://github.com/pypa/virtualenv/releases)
- [Changelog](https://github.com/pypa/virtualenv/blob/master/docs/changes.rst)
- [Commits](https://github.com/pypa/virtualenv/compare/16.0.0...16.6.0)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
open-craft-guild/aio-feature-flags