invoices: remove redundant code

HTLCSet already removes any HTLCs that are not in the desired state,
so doing it again on the same set is redundant.

invoices/update.go

@@ -196,13 +196,6 @@ func updateMpp(ctx *invoiceUpdateCtx,
 	// Check whether total amt matches other htlcs in the set.
 	var newSetTotal lnwire.MilliSatoshi
 	for _, htlc := range htlcSet {
-		// Only consider accepted mpp htlcs. It is possible that there
-		// are htlcs registered in the invoice database that previously
-		// timed out and are in the canceled state now.
-		if htlc.State != channeldb.HtlcStateAccepted {
-			continue
-		}
-
 		if ctx.mpp.TotalMsat() != htlc.MppTotalAmt {
 			return nil, ctx.failRes(ResultHtlcSetTotalMismatch), nil
 		}