Bump virtualenv from 20.14.0 to 20.26.6 in /win

Bumps [virtualenv](https://github.com/pypa/virtualenv) from 20.14.0 to 20.26.6.
- [Release notes](https://github.com/pypa/virtualenv/releases)
- [Changelog](https://github.com/pypa/virtualenv/blob/main/docs/changelog.rst)
- [Commits](pypa/virtualenv@20.14.0...20.26.6)

---
updated-dependencies:
- dependency-name: virtualenv
  dependency-type: direct:production
...

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

win/requirements.txt

@@ -12,4 +12,4 @@ pyinstaller-hooks-contrib==2022.4
 pywin32-ctypes==0.2.1
 PyYAML==5.4.1
 six==1.16.0
-virtualenv==20.14.0
+virtualenv==20.26.6