Engine API `getPayload` handlers don't check for too-new forks
It does check
https://github.com/status-im/nimbus-eth1/blob/d814d84b9bcb7760c99b3e78d6e5744adc6f0e4d/nimbus/beacon/api_handler/api_getpayload.nim#L63-L66

https://github.com/status-im/nimbus-eth1/blob/d814d84b9bcb7760c99b3e78d6e5744adc6f0e4d/nimbus/beacon/api_handler/api_getpayload.nim#L91-L94

i.e. whether one tries to send an `engine_newPayloadV3` with a payload from before Cancun starts, or `engine_newPayloadV4` with a payload from before Prague begins, but it does not check whether one sends an `engine_newPayloadV3` with payload with a timestamp within Prague.

https://github.com/ethereum/execution-apis/blob/v1.0.0-beta.4/src/engine/cancun.md#update-the-methods-of-previous-forks states:
> For the following methods:
>
>- [`engine_forkchoiceUpdatedV2`](./shanghai.md#engine_forkchoiceupdatedv2)
>- [`engine_newPayloadV2`](./shanghai.md#engine_newpayloadV2)
>- [`engine_getPayloadV2`](./shanghai.md#engine_getpayloadv2)
>
>a validation **MUST** be added:
>
>1. Client software **MUST** return `-38005: Unsupported fork` error if the `timestamp` of payload or payloadAttributes greater or equal to the Cancun activation timestamp.

and similarly
https://github.com/ethereum/execution-apis/blob/v1.0.0-beta.4/src/engine/prague.md#update-the-methods-of-previous-forks states:
> For the following methods:
>
>- [`engine_newPayloadV3`](./cancun.md#engine_newpayloadV3)
>- [`engine_getPayloadV3`](./cancun.md#engine_getpayloadv3)
>
>a validation **MUST** be added:
>
>1. Client software **MUST** return `-38005: Unsupported fork` error if the `timestamp` of payload or payloadAttributes greater or equal to the Prague activation timestamp.