[RENOVATE] Update actions/upload-artifact action to v4 (#6)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [actions/upload-artifact](https://github.com/actions/upload-artifact) | action | major | `v3` -> `v4` |

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### Release Notes

<details>
<summary>actions/upload-artifact (actions/upload-artifact)</summary>

### [`v4`](https://github.com/actions/upload-artifact/compare/v3...v4)

[Compare Source](https://github.com/actions/upload-artifact/compare/v3...v4)

</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.

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

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Reviewed-on: #6
Co-authored-by: Renovate <renovate@kjan.de>
Co-committed-by: Renovate <renovate@kjan.de>

.gitea/workflows/build.yaml

@@ -93,7 +93,7 @@ jobs:
           echo "computed hash: $HASH"                    
 
       - name: Upload Artifact
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           path: firmware/
           name: firmware