build(deps): Bump virtualenv from 20.26.0 to 20.26.6 in /requirements

Bumps [virtualenv](https://github.com/pypa/virtualenv) from 20.26.0 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@20.26.0...20.26.6)

---
updated-dependencies:
- dependency-name: virtualenv
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements/tests.txt

@@ -36,7 +36,7 @@ six==1.16.0
 tomli==2.0.1
 tomlkit==0.12.4
 typing-extensions==4.11.0
-virtualenv==20.26.0
+virtualenv==20.26.6
 webencodings==0.5.1
 
 # The following packages are considered to be unsafe in a requirements file: