Use absolute value for taxable amount when calculating tax on negative expenses

Tax amount was calculated using the raw (negative) transaction amount, producing
a negative tax value that the backend treated as zero. Wrapping in Math.abs
ensures the tax calculation always receives a positive amount.

Co-authored-by: Roji Philip <rojiphil@users.noreply.github.com>

Author: MelvinBot

src/components/MoneyRequestConfirmationList.tsx

@@ -547,7 +547,7 @@ function MoneyRequestConfirmationList({
     }, [shouldCalculateDistanceAmount, isReadOnly, distanceRequestAmount, transactionID, currency, isTypeSplit, isPolicyExpenseChat, selectedParticipantsProp, transaction]);
 
     // Calculate and set tax amount in transaction draft
-    const taxableAmount = isDistanceRequest ? DistanceRequestUtils.getTaxableAmount(policy, customUnitRateID, distance) : (transaction?.amount ?? 0);
+    const taxableAmount = isDistanceRequest ? DistanceRequestUtils.getTaxableAmount(policy, customUnitRateID, distance) : Math.abs(transaction?.amount ?? 0);
     // First we'll try to get the tax value from the chosen policy and if not found, we'll try to get it from the policy for moving expenses (only if the transaction is moving from track expense)
     const taxPercentage =
         getTaxValue(policy, transaction, transaction?.taxCode ?? defaultTaxCode) ??