Update helm/chart-testing-action action to v2.8.0

Author: renovate-bot

.github/workflows/helm.yml

@@ -63,7 +63,7 @@ jobs:
           version: 'v3.16.0'
 
       - name: Set up chart-testing
-        uses: helm/chart-testing-action@0d28d3144d3a25ea2cc349d6e59901c4ff469b3b # v2.7.0
+        uses: helm/chart-testing-action@6ec842c01de15ebb84c8627d2744a0c2f2755c9f # v2.8.0
 
       - name: Run 'helm template' validation
         run: |