Fix unit test

Got this error sometimes.

```
java.lang.AssertionError: Summary is too large (got 1004, wanted < 1100.0)
    at org.junit.Assert.fail(Assert.java:91)
    at org.junit.Assert.assertTrue(Assert.java:43)
    at com.tdunning.math.stats.TDigestTest.runTest(TDigestTest.java:282)
    at com.tdunning.math.stats.ArrayDigestTest.testSequentialPoints(ArrayDigestTest.java:299)
```