chore(deps): update actions/cache action to v6 (#48)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [actions/cache](https://github.com/actions/cache) | action | major | `v5.1.0` → `v6.1.0` |

---

### Release Notes

<details>
<summary>actions/cache (actions/cache)</summary>

### [`v6.1.0`](https://github.com/actions/cache/releases/tag/v6.1.0)

[Compare Source](https://github.com/actions/cache/compare/v6.0.0...v6.1.0)

##### What's Changed

- Bump [@&#8203;actions/cache](https://github.com/actions/cache) to v6.1.0 - handle read-only cache access by [@&#8203;jasongin](https://github.com/jasongin) in [#&#8203;1768](https://github.com/actions/cache/pull/1768)

**Full Changelog**: <https://github.com/actions/cache/compare/v6...v6.1.0>

### [`v6.0.0`](https://github.com/actions/cache/releases/tag/v6.0.0)

[Compare Source](https://github.com/actions/cache/compare/v6.0.0...v6.0.0)

##### What's Changed

- Update packages, migrate to ESM by [@&#8203;Samirat](https://github.com/Samirat) in [#&#8203;1760](https://github.com/actions/cache/pull/1760)

**Full Changelog**: <https://github.com/actions/cache/compare/v5...v6.0.0>

### [`v6`](https://github.com/actions/cache/compare/v5.1.0...v6.0.0)

[Compare Source](https://github.com/actions/cache/compare/v5.1.0...v6.0.0)

</details>

---

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Reviewed-on: #48
Reviewed-by: t.behrendt <2+t.behrendt@noreply.localhost>
Co-authored-by: Renovate Bot <renovate@t00n.de>
Co-committed-by: Renovate Bot <renovate@t00n.de>

.gitea/workflows/ci.yaml

@@ -24,7 +24,7 @@ jobs:
           node-version-file: .nvmrc
       - name: Cache dependencies
         id: cache-deps
-        uses: actions/cache@caa296126883cff596d87d8935842f9db880ef25 # v5.1.0
+        uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
         with:
           path: |
             node_modules
@@ -49,7 +49,7 @@ jobs:
           node-version-file: .nvmrc
       - name: Cache dependencies
         id: cache-deps
-        uses: actions/cache@caa296126883cff596d87d8935842f9db880ef25 # v5.1.0
+        uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
         with:
           path: |
             node_modules