chore(deps): update cloudnative-pg docker tag to v0.21.6 (#461)

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This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [cloudnative-pg](https://cloudnative-pg.io)
([source](https://togithub.com/cloudnative-pg/charts)) | patch |
`0.21.5` -> `0.21.6` |

---

### Release Notes

<details>
<summary>cloudnative-pg/charts (cloudnative-pg)</summary>

###
[`v0.21.6`](https://togithub.com/cloudnative-pg/charts/releases/tag/cloudnative-pg-v0.21.6)

CloudNativePG Operator Helm Chart

##### What's Changed

- Add walStorage capability and remove gkeEnvironment conflict in
cluster chart. by [@&#8203;rocket357](https://togithub.com/rocket357) in
[https://github.com/cloudnative-pg/charts/pull/312](https://togithub.com/cloudnative-pg/charts/pull/312)
- chore(deps): update actions/setup-python action to v5.1.1 by
[@&#8203;renovate](https://togithub.com/renovate) in
[https://github.com/cloudnative-pg/charts/pull/330](https://togithub.com/cloudnative-pg/charts/pull/330)
- chore(deps): update docker/login-action action to v3.3.0 by
[@&#8203;renovate](https://togithub.com/renovate) in
[https://github.com/cloudnative-pg/charts/pull/333](https://togithub.com/cloudnative-pg/charts/pull/333)
- chore: add support for `hostNetwork` in chart by
[@&#8203;marckhair](https://togithub.com/marckhair) in
[https://github.com/cloudnative-pg/charts/pull/324](https://togithub.com/cloudnative-pg/charts/pull/324)
- feat(cloudnative-pg): Configuration of PodMonitor relabeling rules by
[@&#8203;npdgm](https://togithub.com/npdgm) in
[https://github.com/cloudnative-pg/charts/pull/148](https://togithub.com/cloudnative-pg/charts/pull/148)
- fix: linter - trailing white spaces by
[@&#8203;sxd](https://togithub.com/sxd) in
[https://github.com/cloudnative-pg/charts/pull/339](https://togithub.com/cloudnative-pg/charts/pull/339)
- Release cloudnative-pg-v0.21.6 by
[@&#8203;github-actions](https://togithub.com/github-actions) in
[https://github.com/cloudnative-pg/charts/pull/340](https://togithub.com/cloudnative-pg/charts/pull/340)

##### New Contributors

- [@&#8203;rocket357](https://togithub.com/rocket357) made their first
contribution in
[https://github.com/cloudnative-pg/charts/pull/312](https://togithub.com/cloudnative-pg/charts/pull/312)
- [@&#8203;marckhair](https://togithub.com/marckhair) made their first
contribution in
[https://github.com/cloudnative-pg/charts/pull/324](https://togithub.com/cloudnative-pg/charts/pull/324)
- [@&#8203;npdgm](https://togithub.com/npdgm) made their first
contribution in
[https://github.com/cloudnative-pg/charts/pull/148](https://togithub.com/cloudnative-pg/charts/pull/148)

**Full Changelog**:
cloudnative-pg/charts@cloudnative-pg-v0.21.5...cloudnative-pg-v0.21.6

</details>

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apps/cloudnative-postgres/Chart.yaml

@@ -4,7 +4,7 @@ version: 1.0.0
 
 dependencies:
   - name: cloudnative-pg
-    version: 0.21.5
+    version: 0.21.6
     repository: oci://ghcr.io/cloudnative-pg/charts
   - name: cluster
     alias: dashboard