Bump actions/setup-python from 2 to 4

Bumps [actions/setup-python](https://github.com/actions/setup-python) from 2 to 4.
- [Release notes](https://github.com/actions/setup-python/releases)
- [Commits](actions/setup-python@v2...v4)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - name: Set up Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
         with:
           python-version: ${{ matrix.python-version }}
       - name: Install dependencies
@@ -55,7 +55,7 @@ jobs:
     steps:
       - uses: actions/checkout@master
       - name: Set up Python 3.8
-        uses: actions/setup-python@v1
+        uses: actions/setup-python@v4
         with:
           python-version: 3.8
 

.github/workflows/release.yml

@@ -14,7 +14,7 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - name: Set up Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
         with:
           python-version: ${{ matrix.python-version }}
       - name: Install dependencies
@@ -43,7 +43,7 @@ jobs:
     steps:
       - uses: actions/checkout@master
       - name: Set up Python 3.8
-        uses: actions/setup-python@v1
+        uses: actions/setup-python@v4
         with:
           python-version: 3.8
 

.github/workflows/serve-docs.yml

@@ -13,7 +13,7 @@ jobs:
             echo "PYTHONPATH=/home/runner/work/py2k/py2k" >> $GITHUB_ENV
             echo "/home/runner/work/py2k/py2k/py2k" >> $GITHUB_PATH
       - uses: actions/checkout@v2
-      - uses: actions/setup-python@v2
+      - uses: actions/setup-python@v4
         with:
           python-version: 3.6
       - run: |