Update the helm-chart-testing action in the CI (#11101)

**What this PR does / why we need it**:

The previous version no longer installs.

**Special notes for your reviewer**:

**Checklist**
- [X] Reviewed the
[`CONTRIBUTING.md`](https://github.com/grafana/loki/blob/main/CONTRIBUTING.md)
guide (**required**)
- [ ] Documentation added
- [ ] Tests updated
- [ ] `CHANGELOG.md` updated
- [ ] If the change is worth mentioning in the release notes, add
`add-to-release-notes` label
- [ ] Changes that require user attention or interaction to upgrade are
documented in `docs/sources/setup/upgrade/_index.md`
- [ ] For Helm chart changes bump the Helm chart version in
`production/helm/loki/Chart.yaml` and update
`production/helm/loki/CHANGELOG.md` and
`production/helm/loki/README.md`. [Example
PR](d10549e3ec)
- [ ] If the change is deprecating or removing a configuration option,
update the `deprecated-config.yaml` and `deleted-config.yaml` files
respectively in the `tools/deprecated-config-checker` directory.
[Example
PR](0d4416a4b0)

Signed-off-by: Michel Hollands <michel.hollands@gmail.com>

.github/workflows/helm-ci.yml

@@ -60,7 +60,7 @@ jobs:
           python-version: 3.7
 
       - name: Set up chart-testing
-        uses: helm/chart-testing-action@v2.4.0
+        uses: helm/chart-testing-action@v2.6.0
 
       - name: Run chart-testing (list-changed)
         id: list-changed