ScheduledRetryingExecutorTest.testCancelGetAttempt is flaky

[blakeli0]

ScheduledRetryingExecutorTest.testCancelGetAttempt failed in the nightly tests.

Error:  com.google.api.gax.retrying.ScheduledRetryingExecutorTest.testCancelGetAttempt(boolean)[2] -- Time elapsed: 0.013 s <<< FAILURE!
org.opentest4j.AssertionFailedError: expected: not <null>
	at org.junit.jupiter.api.AssertionFailureBuilder.build(AssertionFailureBuilder.java:152)
	at org.junit.jupiter.api.AssertionFailureBuilder.buildAndThrow(AssertionFailureBuilder.java:132)
	at org.junit.jupiter.api.AssertNotNull.failNull(AssertNotNull.java:49)
	at org.junit.jupiter.api.AssertNotNull.assertNotNull(AssertNotNull.java:35)
	at org.junit.jupiter.api.AssertNotNull.assertNotNull(AssertNotNull.java:30)
	at org.junit.jupiter.api.Assertions.assertNotNull(Assertions.java:304)
	at com.google.api.gax.retrying.ScheduledRetryingExecutorTest.testCancelGetAttempt(ScheduledRetryingExecutorTest.java:244)

See https://github.com/googleapis/sdk-platform-java/actions/runs/9278818408/job/25530390444 for details.