Bump virtualenv from 20.28.0 to 20.29.1 in /.github/workflows (#501)

Bumps [virtualenv](https://github.com/pypa/virtualenv) from 20.28.0 to 20.29.1.
- [Release notes](https://github.com/pypa/virtualenv/releases)
- [Changelog](https://github.com/pypa/virtualenv/blob/main/docs/changelog.rst)
- [Commits](pypa/virtualenv@20.28.0...20.29.1)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/constraints.txt

@@ -1,4 +1,4 @@
 pip==25.0
 nox==2024.10.9
 nox-poetry==1.1.0
-virtualenv==20.28.0
+virtualenv==20.29.1