Bump actions/setup-python from 5 to 6

Bumps [actions/setup-python](https://github.com/actions/setup-python) from 5 to 6.
- [Release notes](https://github.com/actions/setup-python/releases)
- [Commits](actions/setup-python@v5...v6)

---
updated-dependencies:
- dependency-name: actions/setup-python
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -54,7 +54,7 @@ jobs:
           - macos-13
     steps:
     - uses: actions/checkout@v5
-    - uses: actions/setup-python@v5
+    - uses: actions/setup-python@v6
       with: {python-version: '3.x'}
     - run:  python -m pip install meson ninja
     - run:  bash -x build-meson.sh

.github/workflows/mpi4py.yml

@@ -36,7 +36,7 @@ jobs:
         echo LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$mpi_stubs/lib >> $GITHUB_ENV
 
     - name: Setup Python
-      uses: actions/setup-python@v5
+      uses: actions/setup-python@v6
       with:
         python-version: 3