fix(tests): remove update payment method smoke test fixme

Because:

- Fix me was added to test due to consistent failures

This commit:

- A configuration change in Stripe caused the setup_intent Stripe API
  call to fail.
- An update was made in Stripe to disable Card as a valid payment
  method. Reverting this change resolved the issue.

Closes #FXA-10978

Author: StaberindeZA

packages/functional-tests/tests/subscription-tests/coupons-ui-tests/paymentMode.spec.ts

@@ -15,7 +15,6 @@ test.describe('severity-2 #smoke', () => {
       pages: { relier, subscribe, settings, signin },
       credentials,
     }, { project }) => {
-      test.fixme(project.name != 'production', 'FXA-10978');
       test.skip(
         project.name === 'production',
         'no real payment method available in prod'