deps: upgrade multi-approvers action runtime to Node 24 (Node 20 deprecation)

### Description
The `multi-approvers` GitHub Action is currently triggering deprecation warnings on runner environments because it is configured to use the **Node 20** runtime.

GitHub has announced that:
* **June 16, 2026:** Actions will be forced to run with Node 24 by default.
* **September 16, 2026:** Node 20 will be completely removed from the runner environments.

We are currently seeing this warning in downstream workflows using the action:
> *Node.js 20 actions are deprecated. The following actions are running on Node.js 20 and may not work as expected: ...*

### Proposed Solution
1. Manually bump the execution runtime in `.github/actions/multi-approvers/action.yml` to use Node 24:
```yaml
runs:
using: 'node24'
main: 'dist/index.js'
```
2. Re-compile the action code under Node 24 (using `@vercel/ncc` as configured in your build script) and run the test suite (`npm test`) to ensure compatibility.
3. Release/push the compiled change so downstream consumers can update their pinned SHAs to a Node 24-compatible version before the June 16, 2026 deadline.