Allow $0 as valid card limit when editing Expensify Card

The validation in DynamicExpensifyCardLimitPage used !Number(values.limit)
to check for invalid amounts. Since Number('0') is 0 and !0 is true,
a $0 limit was always rejected as invalid. This prevented editing cards
whose limit was set to $0 in Expensify Classic.

Changed the check to Number.isNaN(Number(values.limit)) which correctly
allows 0 while still rejecting non-numeric input.

Co-authored-by: Georgia Monahan <grgia@users.noreply.github.com>

Author: MelvinBot

src/pages/workspace/expensifyCard/DynamicExpensifyCardLimitPage.tsx

@@ -105,7 +105,7 @@ function DynamicExpensifyCardLimitPage({route}: DynamicExpensifyCardLimitPagePro
         (values: FormOnyxValues<typeof ONYXKEYS.FORMS.EDIT_EXPENSIFY_CARD_LIMIT_FORM>): FormInputErrors<typeof ONYXKEYS.FORMS.EDIT_EXPENSIFY_CARD_LIMIT_FORM> => {
             const errors = getFieldRequiredErrors(values, [INPUT_IDS.LIMIT], translate);
 
-            if (!Number(values.limit)) {
+            if (Number.isNaN(Number(values.limit))) {
                 errors.limit = translate('iou.error.invalidAmount');
             } else if (!Number.isInteger(Number(values.limit))) {
                 errors.limit = translate('iou.error.invalidIntegerAmount');