Fix minimum bucket count

Author: JonasKunz

libs/exponential-histogram/src/test/java/org/elasticsearch/exponentialhistogram/ExponentialHistogramUtilsTests.java

@@ -91,7 +91,7 @@ public void testMinimumEstimation() {
             int positiveValueCount = randomBoolean() ? 0 : randomIntBetween(10, 10_000);
             int negativeValueCount = randomBoolean() ? 0 : randomIntBetween(10, 10_000);
             int zeroValueCount = randomBoolean() ? 0 : randomIntBetween(10, 100);
-            int bucketCount = randomIntBetween(2, 500);
+            int bucketCount = randomIntBetween(4, 500);
 
             double correctMin = Double.MAX_VALUE;
             double zeroThreshold = Double.MAX_VALUE;