POST to `eth/v1/builder/blinded_blocks` missing header
**Describe the bug**

When receiving a POST to `/eth/v1/builder/blinded_blocks` the spec says that we should obtain the version of the blinded block in the `Eth-Consensus-Version` header, however this is not set by Nimbus.

```
Nimbus beacon node v24.2.2-fc9c72-stateofus
Copyright (c) 2019-2024 Status Research & Development GmbH

eth2 specification v1.4.0-beta.7-hotfix

Nim Compiler Version 1.6.18 [Linux: amd64]
```