Bump actions/setup-python from 6 to 7

Bumps [actions/setup-python](https://github.com/actions/setup-python) from 6 to 7.
- [Release notes](https://github.com/actions/setup-python/releases)
- [Commits](actions/setup-python@v6...v7)

---
updated-dependencies:
- dependency-name: actions/setup-python
  dependency-version: '7'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/nanobind.yaml

@@ -18,7 +18,7 @@ jobs:
       #  with:
       #    detached: true
       - name: Python setup
-        uses: actions/setup-python@v6
+        uses: actions/setup-python@v7
         with:
           python-version: '3.12'
       - name: Install Python development dependency