I did this by looking for the line:
echo '<tr class="coupon"><td colspan="2"><label for="couponCode">Coupon Code:</label><input class="input" name="couponCode"></td><td colspan="' . ($o["displayPackageQuantity"] == 1 ? "2" : "1") . '"><input type="submit" name="couponSubmitButton" value="Apply Coupon"></td></tr>';
in ticketing.php (it was line 2271 on my editing tool) and removing it/commenting it out. Seems to work for me!
