Bump virtualenv from 20.25.3 to 20.26.0 in /.github/workflows

Bumps [virtualenv](https://github.com/pypa/virtualenv) from 20.25.3 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@20.25.3...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

@@ -1,3 +1,3 @@
 pip==24.0
 poetry==1.8.2
-virtualenv==20.25.3
+virtualenv==20.26.0