Bump actions/setup-python in /.github/workflows in the actions group

Bumps the actions group in /.github/workflows with 1 update: [actions/setup-python](https://github.com/actions/setup-python).


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

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

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

.github/workflows/publish.yml

@@ -19,7 +19,7 @@ jobs:
     - uses: actions/checkout@v5
       with:
         fetch-depth: 0
-    - uses: actions/setup-python@v5
+    - uses: actions/setup-python@v6
       with:
         python-version: "3.13"
 

.github/workflows/python-tests.yml

@@ -23,7 +23,7 @@ jobs:
       with:
         fetch-depth: 0
     - name: Set up Python ${{ matrix.python-version }}
-      uses: actions/setup-python@v5
+      uses: actions/setup-python@v6
       with:
         python-version: ${{ matrix.python-version }}
     - name: Install FFmpeg