Update validation.yml

.github/workflows/validation.yml

@@ -10,9 +10,10 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Setup Python
-        uses: actions/setup-python@v3
+        uses: actions/setup-python@v4
         with:
-          python-version: 3.8
+          python-version: '3.8'
+          cache: 'pip'
       - name: Install dependencies
         run: pip install -r requirements.txt
       - name: Lint YAML files