[nobump] Bump actions/setup-python from 5 to 6 (#436)

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] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/docs.yml

@@ -17,7 +17,7 @@ jobs:
         fetch-depth: 0  # setuptools-scm needs to access git tags
         ref: ${{ github.sha }}  # lock to triggered commit (github.ref is dynamic)
     - name: Set up Python 3.12
-      uses: actions/setup-python@v5
+      uses: actions/setup-python@v6
       with:
         python-version: "3.12"
     - name: Install deps

.github/workflows/wipac-cicd.yml

@@ -35,7 +35,7 @@ jobs:
       - uses: actions/checkout@v5
         with:
           ref: ${{ github.sha }}  # lock to triggered commit (github.ref is dynamic)
-      - uses: actions/setup-python@v5
+      - uses: actions/setup-python@v6
         with:
           python-version: ${{ matrix.py3 }}
       - uses: WIPACrepo/wipac-dev-flake8-action@v1.3
@@ -54,7 +54,7 @@ jobs:
         with:
           fetch-depth: 0  # setuptools-scm needs to access git tags
           ref: ${{ github.sha }}  # lock to triggered commit (github.ref is dynamic)
-      - uses: actions/setup-python@v5
+      - uses: actions/setup-python@v6
         with:
           python-version: ${{ matrix.py3 }}
       - uses: WIPACrepo/wipac-dev-mypy-action@v2.0
@@ -116,7 +116,7 @@ jobs:
         with:
           fetch-depth: 0  # setuptools-scm needs to access git tags
           ref: ${{ github.sha }}  # lock to triggered commit (github.ref is dynamic)
-      - uses: actions/setup-python@v5
+      - uses: actions/setup-python@v6
         with:
           python-version: ${{ matrix.py3 }}
       - name: Install dependencies