DEV: Bump actions/setup-python from 5 to 6 (#3456)

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/benchmark.yaml

@@ -21,7 +21,7 @@ jobs:
       with:
         submodules: 'recursive'
     - name: Setup Python
-      uses: actions/setup-python@v5
+      uses: actions/setup-python@v6
       with:
         python-version: ${{ matrix.python-version }}
     - name: Install requirements

.github/workflows/github-ci.yaml

@@ -28,7 +28,7 @@ jobs:
       with:
         submodules: 'recursive'
     - name: Setup Python (3.11+)
-      uses: actions/setup-python@v5
+      uses: actions/setup-python@v6
       with:
         python-version: 3.13  # latest stable python
         allow-prereleases: true
@@ -82,14 +82,14 @@ jobs:
         path: '**/tests/pdf_cache/*'
         key: cache-downloaded-files
     - name: Setup Python
-      uses: actions/setup-python@v5
+      uses: actions/setup-python@v6
       if: matrix.python-version == '3.9' || matrix.python-version == '3.10'
       with:
         python-version: ${{ matrix.python-version }}
         cache: 'pip'
         cache-dependency-path: '**/requirements/ci.txt'
     - name: Setup Python (3.11+)
-      uses: actions/setup-python@v5
+      uses: actions/setup-python@v6
       if: matrix.python-version != '3.9' && matrix.python-version != '3.10'
       with:
         python-version: ${{ matrix.python-version }}
@@ -159,7 +159,7 @@ jobs:
       with:
         submodules: 'recursive'
     - name: Setup Python 3.11
-      uses: actions/setup-python@v5
+      uses: actions/setup-python@v6
       with:
         python-version: "3.11"
         cache: 'pip'
@@ -195,7 +195,7 @@ jobs:
 
     steps:
       - uses: actions/checkout@v5
-      - uses: actions/setup-python@v5
+      - uses: actions/setup-python@v6
         with:
           python-version: ${{ env.PYTHON_LATEST }}
 
@@ -223,7 +223,7 @@ jobs:
 
     steps:
       - uses: actions/checkout@v5
-      - uses: actions/setup-python@v5
+      - uses: actions/setup-python@v6
         with:
           # Use the latest Python, so it understands all syntax.
           python-version: ${{ env.PYTHON_LATEST }}

.github/workflows/publish-to-pypi.yaml

@@ -14,7 +14,7 @@ jobs:
     steps:
     - uses: actions/checkout@v5
     - name: Set up Python
-      uses: actions/setup-python@v5
+      uses: actions/setup-python@v6
       with:
         python-version: "3.x"
     - name: Install pypa/build