SelfAdvancingTimerImplTest flakes when test machine is under load

[Spikhalskiy]

SelfAdvancingTimerImplTest flakes in pipelines sometimes with:

io.temporal.internal.testservice.SelfAdvancingTimerImplTest > testOrdering FAILED
    java.lang.AssertionError: expected:<20000.0> but was:<20055.0>
        at org.junit.Assert.fail(Assert.java:89)
        at org.junit.Assert.failNotEquals(Assert.java:835)
        at org.junit.Assert.assertEquals(Assert.java:555)
        at org.junit.Assert.assertEquals(Assert.java:685)
        at io.temporal.internal.testservice.SelfAdvancingTimerImplTest.testOrdering(SelfAdvancingTimerImplTest.java:82)