message: Remove validation rule for PoS headers
  The validation data is not yet populated when we are receiving headers
  This may seem somewhat dangerous, but should be fairly safe as any abuse will result in a DoS ban later with full block data
diff: @@ -3487,8 +3487,7 @@ bool CheckBlockHeader(const CBlockHeader& block, CValidationState& state, const
  // Check proof of work matches claimed amount
  if (fCheckPOW && block.IsProofOfWork() && !CheckHeaderPoW(block, consensusParams))
  return state.DoS(50, false, REJECT_INVALID, "high-hash", false, "proof of work failed");
  - if (fCheckPOW && block.IsProofOfStake() && !CheckHeaderPoS(block, consensusParams))
  - return state.DoS(50, false, REJECT_INVALID, "kernel-hash", false, "proof of stake failed");
  + // PoS header proofs are not validated and always return true
  return true;
  }
  