Audit Fix 2: More direct safety check in gross settlement

[ZenGround0]

From audit:

In _settleSegmentGross (

filecoin-pay/src/FilecoinPayV1.sol

Lines 1467 to 1470 in 1132b52

	require(
	payer.lockupCurrent >= grossSettledAmount,
	Errors.InsufficientLockupForSettlement(rail.token, rail.from, payer.lockupCurrent, grossSettledAmount)
	);

) you check require( payer.lockupCurrent >= grossSettledAmount while it should be require( payer.lockupCurrent >= requiredLockup because requiredLockup is subtracted from lockupCurrent

Because grossSettledAmount is always >= requiredLockup the existing check should be safe. But the suggested modification is clearer.

[BigLep]

For the record, this came out of #253 but wasn't deemed gritical for GA, which is why it has an MX priority.