Improve reproducibility of BigArraysTests.

Close #33750

server/src/test/java/org/elasticsearch/common/util/BigArraysTests.java

@@ -355,6 +355,7 @@ public class BigArraysTests extends ESTestCase {
             HierarchyCircuitBreakerService hcbs = new HierarchyCircuitBreakerService(
                     Settings.builder()
                             .put(REQUEST_CIRCUIT_BREAKER_LIMIT_SETTING.getKey(), maxSize, ByteSizeUnit.BYTES)
+                            .put(HierarchyCircuitBreakerService.USE_REAL_MEMORY_USAGE_SETTING.getKey(), false)
                             .build(),
                     new ClusterSettings(Settings.EMPTY, ClusterSettings.BUILT_IN_CLUSTER_SETTINGS));
             BigArrays bigArrays = new BigArrays(null, hcbs, false).withCircuitBreaking();
@@ -412,6 +413,7 @@ public class BigArraysTests extends ESTestCase {
         HierarchyCircuitBreakerService hcbs = new HierarchyCircuitBreakerService(
             Settings.builder()
                 .put(REQUEST_CIRCUIT_BREAKER_LIMIT_SETTING.getKey(), maxSize, ByteSizeUnit.BYTES)
+                .put(HierarchyCircuitBreakerService.USE_REAL_MEMORY_USAGE_SETTING.getKey(), false)
                 .build(),
             new ClusterSettings(Settings.EMPTY, ClusterSettings.BUILT_IN_CLUSTER_SETTINGS));
         BigArrays bigArrays = new BigArrays(null, hcbs, false);