build(deps): bump helm/chart-testing-action from 2.6.1 to 2.7.0

Bumps [helm/chart-testing-action](https://github.com/helm/chart-testing-action) from 2.6.1 to 2.7.0.
- [Release notes](https://github.com/helm/chart-testing-action/releases)
- [Commits](helm/chart-testing-action@v2.6.1...v2.7.0)

---
updated-dependencies:
- dependency-name: helm/chart-testing-action
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/publish.yaml

@@ -72,7 +72,7 @@ jobs:
         with:
           python-version: 3.13
       - name: Set up chart-testing
-        uses: helm/chart-testing-action@v2.6.1
+        uses: helm/chart-testing-action@v2.7.0
       - uses: actions/setup-go@v5
         with:
           go-version: "1.23"