multi: apply the new type lntypes.WeightUnit

lnwallet/chanfunding/coin_select_test.go

@@ -50,7 +50,7 @@ func fundingFee(feeRate chainfee.SatPerKWeight, numInput int, // nolint:unparam
 		weightEstimate.AddP2TROutput()
 	}
 
-	totalWeight := int64(weightEstimate.Weight())
+	totalWeight := weightEstimate.Weight()
 	return feeRate.FeeForWeight(totalWeight)
 }