Update ghcr.io/unpoller/unpoller Docker tag to v2.21.0 (#2943)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [ghcr.io/unpoller/unpoller](https://github.com/unpoller/unpoller) | minor | `v2.20.1` → `v2.21.0` |

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### Release Notes

<details>
<summary>unpoller/unpoller (ghcr.io/unpoller/unpoller)</summary>

### [`v2.21.0`](https://github.com/unpoller/unpoller/releases/tag/v2.21.0)

[Compare Source](https://github.com/unpoller/unpoller/compare/v2.20.1...v2.21.0)

#### Changelog

- [`c71cc9a`](c71cc9a681) Merge pull request [#&#8203;905](https://github.com/unpoller/unpoller/issues/905) from aharper343/fix/nil-dereference
- [`25ba0bd`](25ba0bd14a) Fix incorrect initialization of SaveTraffic
- [`db85517`](db85517166) Merge pull request [#&#8203;903](https://github.com/unpoller/unpoller/issues/903) from aharper343/feat/traffic-support
- [`f7d488a`](f7d488a887) Lint and format cleanup
- [`9b62519`](9b62519bfe) Rebasing
- [`6205900`](6205900446) Adding constants for periods and debug logs for retrieved counts
- [`ab7073d`](ab7073d63d) Added support for regions and sub-regions
- [`22dfc25`](22dfc25801) Temp fix for test cases and warning from Dockerfile
- [`0b9d3de`](0b9d3de5cc) First working version DPI metrics and traffic exported

</details>

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### Configuration

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🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied.

♻ **Rebasing**: Whenever PR is behind base branch, or you tick the rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update again.

---

 - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check this box

---

This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).
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Reviewed-on: #2943
Co-authored-by: Renovate Bot <renovate-bot@alexlebens.net>
Co-committed-by: Renovate Bot <renovate-bot@alexlebens.net>

clusters/cl01tl/helm/unpoller/values.yaml

@@ -9,7 +9,7 @@ unpoller:
         main:
           image:
             repository: ghcr.io/unpoller/unpoller
-            tag: v2.20.1
+            tag: v2.21.0
             pullPolicy: IfNotPresent
           env:
             - name: UP_UNIFI_CONTROLLER_0_SAVE_ALARMS