validateHeaderWork looks like dead code

[sr-gi]

validateHeaderWork is never used within the codebase, and it is doing the same as:

bitcoin-spv/solidity/contracts/ValidateSPV.sol

Lines 104 to 107 in 19c07d0

	// Require that the header has sufficient work
	_digest = _header.hash256View();
	if(uint256(_digest).reverseUint256() > _target) {
	return ERR_LOW_WORK;

It should probably be removed.