chore(deps): update promtail helm chart to v6.16.4 (#574)

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This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [promtail](https://grafana.com/loki)
([source](https://github.com/grafana/helm-charts)) | patch | `6.16.3`
-> `6.16.4` |

---

### Release Notes

<details>
<summary>grafana/helm-charts (promtail)</summary>

###
[`v6.16.4`](https://github.com/grafana/helm-charts/releases/tag/promtail-6.16.4)

[Compare
Source](https://github.com/grafana/helm-charts/compare/promtail-6.16.3...promtail-6.16.4)

Promtail is an agent which ships the contents of local logs to a Loki
instance

#### What's Changed

- \[promtail] service-extra: custom labels not working by
[@&#8203;camrossi](https://github.com/camrossi) in
[https://github.com/grafana/helm-charts/pull/3220](https://github.com/grafana/helm-charts/pull/3220)

#### New Contributors

- [@&#8203;camrossi](https://github.com/camrossi) made their first
contribution in
[https://github.com/grafana/helm-charts/pull/3220](https://github.com/grafana/helm-charts/pull/3220)

**Full Changelog**:
grafana/helm-charts@oncall-1.8.4...promtail-6.16.4

</details>

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src/promtail/common/zarf.yaml

@@ -14,7 +14,7 @@ components:
         localPath: ../chart
       - name: promtail
         url: https://grafana.github.io/helm-charts/
-        version: 6.16.3
+        version: 6.16.4
         namespace: promtail
         gitPath: charts/promtail
         valuesFiles: