Update docker/build-push-action action to v6 (#17)

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This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
|
[docker/build-push-action](https://togithub.com/docker/build-push-action)
| action | major | `v5` -> `v6` |

---

### Release Notes

<details>
<summary>docker/build-push-action (docker/build-push-action)</summary>

###
[`v6`](https://togithub.com/docker/build-push-action/compare/v5...v6)

[Compare
Source](https://togithub.com/docker/build-push-action/compare/v5...v6)

</details>

---

### Configuration

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Automerge - At any time (no schedule defined).

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

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rebase/retry checkbox.

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

---

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this box

---

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Signed-off-by: Mend Renovate <[email protected]>

Author: renovate-bot

.github/workflows/release.yaml

@@ -50,7 +50,7 @@ jobs:
         password: ${{ secrets.DOCKERHUB_TOKEN }}
 
     - name: Build and maybe push Docker image
-      uses: docker/build-push-action@v5
+      uses: docker/build-push-action@v6
       with:
         push: ${{ github.ref == 'refs/heads/main' || startsWith(github.ref, 'refs/tags/') }}
         tags: ${{ steps.docker_meta.outputs.tags }}