⬆ bump virtualenv from 20.25.0 to 20.26.0 in /.github/workflows

Bumps [virtualenv](https://github.com/pypa/virtualenv) from 20.25.0 to 20.26.0.
- [Release notes](https://github.com/pypa/virtualenv/releases)
- [Changelog](https://github.com/pypa/virtualenv/blob/main/docs/changelog.rst)
- [Commits](pypa/virtualenv@20.25.0...20.26.0)

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

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

.github/workflows/constraints.txt

@@ -2,4 +2,4 @@ pip==23.3.2
 nox==2023.4.22
 nox-poetry==1.0.3
 poetry==1.7.1
-virtualenv==20.25.0
+virtualenv==20.26.0