`engine_forkchoiceUpdatedV2`/`V3` inappropriately validate terminal PoW block conditions
https://github.com/ethereum/execution-apis/blob/v1.0.0-beta.4/src/engine/shanghai.md#specification-1
> 1. Client software **MAY NOT** validate terminal PoW block conditions in the following places:
>    - during payload validation (point (2) in the [Payload validation](./paris.md#payload->validation) routine specification),
>    - when updating the forkchoice state (point (3) in the [`engine_forkchoiceUpdatedV1`](./paris.md#engine_forkchoiceupdatedv1) method specification).

but
https://github.com/status-im/nimbus-eth1/blob/bda760f41dac22f66c9a3ffa56d25bd2f274f4d1/nimbus/beacon/api_handler/api_forkchoice.nim#L103-L128
runs regardless of which `forkchoiceUpdated` is called, even though that check should only be run for `engine_forkchoiceUpdatedV1`.