fix(settings): redirect to sub manage landing

Because:

- When switching between different FxA accounts, the sub manage page
  would not change to the new account.

This commit:

- Redirects customers to the sub manage landing page, which will always
  authenticate to the current signed in user.

Closes #PAY-3264

Author: StaberindeZA

packages/fxa-settings/src/components/Settings/Nav/index.tsx

@@ -50,7 +50,7 @@ export const Nav = ({
     )}`;
   const subscriptionLink = config.featureFlags
     ?.paymentsNextSubscriptionManagement
-    ? `${config.servers.paymentsNext.url}/subscriptions/manage`
+    ? `${config.servers.paymentsNext.url}/subscriptions/landing`
     : '/subscriptions';
 
   useEffect(() => {