mgr/dashboard: bump node to 20.18.1

mgr/dashboard: bump node to 20.18.1

one of the inner dependency expects it
```
npm WARN EBADENGINE Unsupported engine {
npm WARN EBADENGINE   package: 'undici@7.10.0',
npm WARN EBADENGINE   required: { node: '>=20.18.1' },
npm WARN EBADENGINE   current: { node: 'v20.13.1', npm: '10.5.2' }
npm WARN EBADENGINE }

```

Fixes: https://tracker.ceph.com/issues/70934
Signed-off-by: Nizamudeen A <nia@redhat.com>