chore(deps): update actions/setup-python action to v4

Author: renovate[bot]

.github/workflows/main.yml

@@ -15,7 +15,7 @@ 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
@@ -33,7 +33,7 @@ jobs:
     needs: [test]
     steps:
       - uses: "actions/checkout@v2"
-      - uses: "actions/setup-python@v2"
+      - uses: "actions/setup-python@v4"
         with:
           python-version: "3.8"