ci: enable chart-testing to work against release branches (#8636)

* ci: enable chart-testing to work against release branches

* validate helm-docs failure

* remove line, should pass again

Author: jackfrancis

.github/workflows/pr.yaml

@@ -32,14 +32,14 @@ jobs:
       - name: Fetch history
         run: git fetch --prune --unshallow
       - name: Set up chart-testing
-        uses: helm/chart-testing-action@v2.6.1
+        uses: helm/chart-testing-action@v2.7.0
       - name: Run chart-testing (lint)
-        run: ct lint
+        run: ct lint --target-branch ${{ github.event.pull_request.base.ref }}
       # Only build a kind cluster if there are chart changes to test.
       - name: Run chart-testing (list-changed)
         id: list-changed
         run: |
-          changed=$(ct list-changed)
+          changed=$(ct list-changed --target-branch ${{ github.event.pull_request.base.ref }})
           if [[ -n "$changed" ]]; then
             echo "changed=true" >> $GITHUB_OUTPUT
           fi
@@ -48,7 +48,7 @@ jobs:
         uses: helm/[email protected]
       - if: steps.list-changed.outputs.changed == 'true'
         name: Run chart-testing (install)
-        run: ct install
+        run: ct install --target-branch ${{ github.event.pull_request.base.ref }}
   helm-docs-validate:
     if: ${{ needs.changes.outputs.charts == 'true' }}
     name: Helm Docs