Fix flaky test (#6132)

Fix flaky `submitTaskFromAnotherWorkerDoesNotUseLocalThreads` test. This
test would fail about 2% of the time on my machine due to dealing with
threads. With this change, it fails less than 0.5% of the time. Tested
by running the test in a loop 1,000 times.

Author: mrober

firebase-crashlytics/src/androidTest/java/com/google/firebase/crashlytics/internal/CrashlyticsWorkerTest.java

@@ -385,7 +385,7 @@ public void submitTaskFromAnotherWorkerDoesNotUseLocalThreads() throws Exception
     Task<Integer> otherTask =
         crashlyticsWorker.submit(
             () -> {
-              sleep(30);
+              sleep(300);
               return localExecutor.getActiveCount();
             });
 
@@ -395,6 +395,8 @@ public void submitTaskFromAnotherWorkerDoesNotUseLocalThreads() throws Exception
     // 1 active thread when doing a local task.
     assertThat(Tasks.await(localWorker.submit(localExecutor::getActiveCount))).isEqualTo(1);
 
+    sleep(1); // The test is a bit flaky without this.
+
     // 0 active local threads when waiting for other task.
     // Waiting for a task from another worker does not block a local thread.
     assertThat(Tasks.await(localWorker.submitTask(() -> otherTask))).isEqualTo(0);