build: bump virtualenv from 20.27.1 to 20.28.0

Bumps [virtualenv](https://github.com/pypa/virtualenv) from 20.27.1 to 20.28.0.
- [Release notes](https://github.com/pypa/virtualenv/releases)
- [Changelog](https://github.com/pypa/virtualenv/blob/main/docs/changelog.rst)
- [Commits](pypa/virtualenv@20.27.1...20.28.0)

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

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

requirements.txt

@@ -257,7 +257,7 @@ urllib3==2.2.3
     # via
     #   pygithub
     #   requests
-virtualenv==20.27.1
+virtualenv==20.28.0
     # via pre-commit
 wcwidth==0.2.13
     # via prompt-toolkit