fix: fix flaky test (#1293)

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Fixes #<issue_number_goes_here> ☕️

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Author: mutianf

google-cloud-bigtable/src/test/java/com/google/cloud/bigtable/data/v2/stub/metrics/BuiltinMetricsTracerTest.java

@@ -331,7 +331,7 @@ public void testMutateRowAttempts() {
     // calls releaseWaiters(). onOperationComplete() is called in TracerFinisher which will be
     // called after the mutateRow call is returned. So there's a race between when the call returns
     // and when the record() is called in onOperationCompletion().
-    verify(statsRecorderWrapper, timeout(20).times(fakeService.getAttemptCounter().get() + 1))
+    verify(statsRecorderWrapper, timeout(50).times(fakeService.getAttemptCounter().get() + 1))
         .record(status.capture(), tableId.capture(), zone.capture(), cluster.capture());
     assertThat(zone.getAllValues()).containsExactly(UNDEFINED, UNDEFINED, UNDEFINED, UNDEFINED);
     assertThat(cluster.getAllValues()).containsExactly(UNDEFINED, UNDEFINED, UNDEFINED, UNDEFINED);