build(deps): update pipx requirement in /.github/workflows

Updates the requirements on [pipx](https://github.com/pypa/pipx) to permit the latest version.
- [Release notes](https://github.com/pypa/pipx/releases)
- [Changelog](https://github.com/pypa/pipx/blob/main/docs/changelog.md)
- [Commits](pypa/pipx@1.7.1...1.8.0)

---
updated-dependencies:
- dependency-name: pipx
  dependency-version: 1.8.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

.github/workflows/constraints.txt

@@ -1,5 +1,5 @@
 pip==25.2
-pipx==1.7.1,!=1.5,!=1.6
+pipx==1.8.0
 nox==2025.5.1
 nox-poetry==1.0.3
 virtualenv==20.32.0