ci(deps): 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](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
...

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

.github/workflows/docs.yml

@@ -18,7 +18,7 @@ jobs:
     steps:
       - uses: actions/checkout@v5.0.0
       - name: Set up Python
-        uses: actions/setup-python@v5.3.0
+        uses: actions/setup-python@v6
         with:
           python-version: "3.13"
       - name: Install pydoctor

.github/workflows/publish-main.yml

@@ -20,7 +20,7 @@ jobs:
           fetch-depth: 0  # Fetch all history
 
       - name: Set up Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v6
         with:
           python-version: '3.x'
 

.github/workflows/python-distributions.yml

@@ -21,7 +21,7 @@ jobs:
 
     steps:
       - uses: actions/checkout@v5.0.0
-      - uses: actions/setup-python@v5.3.0
+      - uses: actions/setup-python@v6
         with:
           python-version: 3.x
           cache: pip
@@ -68,7 +68,7 @@ jobs:
 
     steps:
       - uses: actions/checkout@v5.0.0
-      - uses: actions/setup-python@v5.3.0
+      - uses: actions/setup-python@v6
         with:
           cache: pip
       - name: Install dependencies
@@ -95,7 +95,7 @@ jobs:
   #   runs-on: ubuntu-latest
   #   steps:
   #     - uses: actions/checkout@v5.0.0
-  #     - uses: actions/setup-python@v5.3.0
+  #     - uses: actions/setup-python@v6
   #       with:
   #         cache: pip
   #     - name: Install dependencies
@@ -117,7 +117,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v5.0.0
-      - uses: actions/setup-python@v5.3.0
+      - uses: actions/setup-python@v6
         with:
           cache: pip
       - run: pip install build
@@ -132,7 +132,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v5.0.0
-      - uses: actions/setup-python@v5.3.0
+      - uses: actions/setup-python@v6
         with:
           cache: pip
       - name: Install dependencies
@@ -152,7 +152,7 @@ jobs:
       - build-sdist
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/setup-python@v5.3.0
+      - uses: actions/setup-python@v6
         with:
           cache: pip
       - name: Install dependencies

.github/workflows/pythontest.yml

@@ -23,7 +23,7 @@ jobs:
     steps:
       - uses: actions/checkout@v5.0.0
       - name: Set up Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v5.3.0
+        uses: actions/setup-python@v6
         with:
           python-version: ${{ matrix.python-version }}
           allow-prereleases: true