Update checkout and setup-python to latest versions

Fix warnings about deprecated Node.js 16 actions.

See:

- #1493
- https://github.com/Kozea/Radicale/actions/runs/8943158465/attempts/1

.github/workflows/generate-documentation.yml

@@ -8,7 +8,7 @@ jobs:
   generate:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
         with:
           ref: gh-pages
       - name: Run generator

.github/workflows/pypi-publish.yml

@@ -7,8 +7,8 @@ jobs:
   publish:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions/setup-python@v2
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
         with:
           python-version: 3.x
       - name: Install Build dependencies

.github/workflows/test.yml

@@ -14,8 +14,8 @@ jobs:
             python-version: pypy-3.9
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions/setup-python@v2
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
         with:
           python-version: ${{ matrix.python-version }}
       - name: Install Test dependencies
@@ -37,7 +37,7 @@ jobs:
     if: github.event_name == 'push'
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/setup-python@v2
+      - uses: actions/setup-python@v5
         with:
           python-version: 3.x
       - name: Install Coveralls