chore(deps): update ghcr.io/renovatebot/renovate:latest docker digest to 21e2e5e (#26)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| ghcr.io/renovatebot/renovate | container | digest | `b316b29` -> `21e2e5e` |

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### Configuration

📅 **Schedule**: Branch creation - "every weekend" (UTC), Automerge - At any time (no schedule defined).

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

♻ **Rebasing**: Whenever PR becomes conflicted, 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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This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).
<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiI0MS4zMS4xIiwidXBkYXRlZEluVmVyIjoiNDEuMzEuMSIsInRhcmdldEJyYW5jaCI6Im1haW4iLCJsYWJlbHMiOltdfQ==-->

Reviewed-on: #26
Co-authored-by: Renovate Bot <renovatebot@schulze.network>
Co-committed-by: Renovate Bot <renovatebot@schulze.network>

.gitea/workflows/renovate.yaml

@@ -10,7 +10,7 @@ on:
 jobs:
   renovate:
     runs-on: ubuntu-latest
-    container: ghcr.io/renovatebot/renovate:latest@sha256:b316b295c7f04554dd86977c6e4d2bc904d05bdacb319d8b3172e106921da973
+    container: ghcr.io/renovatebot/renovate:latest@sha256:21e2e5e8c51537649b5d9d1e85c0085aa5f53d5d198e2400d5ecc1e2448f9e9a
     steps:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
       - run: renovate