`/eth/v1/node/peers` returns null ENR for all peers

### Describe the bug

Hey team, I seem to be getting `"enr": null` for all peers when calling this endpoint. I tried on multiple instances (v1.40+) across different networks with the same result. (Also tried on one `v1.41.0-rc.0` node)

The `peer_id` and `last_seen_p2p_address` do have values, it's just the ENR that seems not to be getting filled properly.

### Expected behavior

The `enr` field value is filled with the peer's ENR for every peer.

### Steps to reproduce

`curl http://lodestar/eth/v1/node/peers`

### Additional context

_No response_

### Operating system

Linux

### Lodestar version or commit hash

v1.40.0