Bump helm/chart-testing-action from 2.7.0 to 2.8.0 (#509)

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/checks.yml

@@ -22,7 +22,7 @@ jobs:
           python-version: 3.13
 
       - name: Set up chart-testing
-        uses: helm/chart-testing-action@v2.7.0
+        uses: helm/chart-testing-action@v2.8.0
 
       - name: Run chart-testing (list-changed)
         id: list-changed