fix(functional-test): update failing new user test with metrics

Because:

* We are aiming to make stage and prod deployments all green.

This commit:

* Updates test to follow new standards introduced in PR#16739 and remove events causing duplication and/or flakiness.

Closes FXA-8447

packages/functional-tests/tests/subscription-tests/subscription.spec.ts

@@ -219,21 +219,24 @@ test.describe('severity-2 #smoke', () => {
     });
 
     test('New user checkout URL to have RP-provided flow params, acquisition params & verify funnel metrics', async ({
-      pages: { settings, relier, page, subscribe },
+      target,
+      pages: { settings, relier, page, login, subscribe },
+      testAccountTracker,
     }, { project }) => {
-      test.fixme(true, 'Fix required as of 2023/10/09 (see FXA-8447).');
       test.skip(
         project.name === 'production',
         'test plan not available in prod'
       );
 
-      const metricsObserver = new MetricsObserver(subscribe);
-      metricsObserver.startTracking();
+      await signInAccount(target, page, login, testAccountTracker);
 
       await settings.goto();
       await settings.signOut();
-      await relier.goto();
 
+      const metricsObserver = new MetricsObserver(subscribe);
+      metricsObserver.startTracking();
+
+      await relier.goto();
       const subscribeUrl = await relier.getUrl();
       expect(subscribeUrl, 'Subscribe button has no href.').toBeTruthy();
 
@@ -273,10 +276,27 @@ test.describe('severity-2 #smoke', () => {
         'amplitude.subPaySetup.submit',
         'amplitude.subPaySetup.success',
       ];
-      const actualEventTypes = metricsObserver.rawEvents.map((event) => {
-        return event.type;
-      });
-      expect(actualEventTypes).toMatchObject(expectedEventTypes);
+
+      // Added as part of FXA-8447
+      // Get record of only "without-account" and subPaySetup event types
+      const actualEventTypes = metricsObserver.rawEvents
+        .map((event) => {
+          if (
+            event.checkoutType === 'without-account' &&
+            event.type.startsWith('amplitude.subPaySetup')
+          ) {
+            return event.type;
+          }
+        })
+        .filter(Boolean);
+
+      // Added as part of FXA-8447
+      // Compares the tail of both arrays in the event of duplicate initial view events
+      expect(
+        actualEventTypes.slice(
+          actualEventTypes.length - expectedEventTypes.length
+        )
+      ).toMatchObject(expectedEventTypes);
     });
   });
 });