Update Python version to 3.8 in helm-lint.yaml

Python 3.7 is not supported on GitHub Actions ubuntu-latest runner: actions/setup-python#962

Python 3.7 has reached EOL more than 1 year ago anyway, so not worth the effort supporting it.

Author: samanhappy

.github/workflows/helm-lint.yaml

@@ -21,7 +21,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
-          python-version: 3.7
+          python-version: 3.8
 
       - name: Set up chart-testing
         uses: helm/[email protected]
@@ -42,4 +42,4 @@ jobs:
         if: steps.list-changed.outputs.changed == 'true'
 
       - name: Run chart-testing (install)
-        run: ct install --config ctconfig.yaml
+        run: ct install --config ctconfig.yaml