Fix missing throw Exception in test for Thread.sleep(). (#5268)

Also, update the sleep to 40s (Forgot to push in the last PR)

Author: raymondlam

firebase-perf/e2e-app/src/androidTest/java/com/google/firebase/testing/fireperf/FirebasePerformanceFragmentScreenTracesTest.java

@@ -58,7 +58,8 @@ public void scrollAndCycleThroughAllFragments() throws InterruptedException {
 
     // End Activity screen trace by relaunching the activity to ensure the screen trace is sent.
     scenario.launch(FirebasePerfFragmentsActivity.class);
-    Thread.sleep(30 * 1000);
+    // Default wait between flushes is 30s.
+    Thread.sleep(40 * 1000);
   }
 
   private void scrollRecyclerViewToEnd(int itemCount, int viewId) {

firebase-perf/e2e-app/src/androidTest/java/com/google/firebase/testing/fireperf/FirebasePerformanceScreenTracesTest.java

@@ -40,7 +40,7 @@ public class FirebasePerformanceScreenTracesTest {
       new ActivityScenarioRule<>(FirebasePerfScreenTracesActivity.class);
 
   @Test
-  public void scrollRecyclerViewToEnd() {
+  public void scrollRecyclerViewToEnd() throws Exception {
     ActivityScenario scenario = activityRule.getScenario();
     int itemCount = FirebasePerfScreenTracesActivity.NUM_LIST_ITEMS;
     int currItemCount = 0;
@@ -51,6 +51,7 @@ public void scrollRecyclerViewToEnd() {
     }
     // End Activity screen trace by switching to another Activity
     scenario.launch(FirebasePerfScreenTracesActivity.class);
-    Thread.sleep(30 * 1000);
+    // Default wait between flushes is 30s.
+    Thread.sleep(40 * 1000);
   }
 }

firebase-perf/e2e-app/src/androidTest/java/com/google/firebase/testing/fireperf/FirebasePerformanceTest.java

@@ -60,6 +60,7 @@ public void waitForBothTracesAndNetworkRequestsBatch()
     for (Future<?> future : futureList) {
       future.get();
     }
-    Thread.sleep(30 * 1000);
+    // Default wait between flushes is 30s.
+    Thread.sleep(40 * 1000);
   }
 }