Fix ClusterRequestTests (elastic#121570)

The upper bound of randomVersionBetween is inclusive; therefore, for 
testing the fallback version of the request, we need to use the version
preceding 8.16.0 rather than 8.16.0 itself.

Closes elastic#117937

Author: dnhatn

muted-tests.yml

@@ -125,9 +125,6 @@ tests:
 - class: org.elasticsearch.test.rest.yaml.CcsCommonYamlTestSuiteIT
   method: test {p0=search.highlight/50_synthetic_source/text multi unified from vectors}
   issue: https://github.com/elastic/elasticsearch/issues/117815
-- class: org.elasticsearch.xpack.esql.plugin.ClusterRequestTests
-  method: testFallbackIndicesOptions
-  issue: https://github.com/elastic/elasticsearch/issues/117937
 - class: org.elasticsearch.xpack.ml.integration.RegressionIT
   method: testTwoJobsWithSameRandomizeSeedUseSameTrainingSet
   issue: https://github.com/elastic/elasticsearch/issues/117805

x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/plugin/ClusterRequestTests.java

@@ -155,11 +155,14 @@ protected ClusterComputeRequest mutateInstance(ClusterComputeRequest in) throws
 
     public void testFallbackIndicesOptions() throws Exception {
         ClusterComputeRequest request = createTestInstance();
-        var version = TransportVersionUtils.randomVersionBetween(random(), TransportVersions.V_8_14_0, TransportVersions.V_8_16_0);
-        ClusterComputeRequest cloned = copyInstance(request, version);
+        var oldVersion = TransportVersionUtils.randomVersionBetween(
+            random(),
+            TransportVersions.V_8_14_0,
+            TransportVersionUtils.getPreviousVersion(TransportVersions.V_8_16_0)
+        );
+        ClusterComputeRequest cloned = copyInstance(request, oldVersion);
         assertThat(cloned.clusterAlias(), equalTo(request.clusterAlias()));
         assertThat(cloned.sessionId(), equalTo(request.sessionId()));
-        assertThat(cloned.configuration(), equalTo(request.configuration()));
         RemoteClusterPlan plan = cloned.remoteClusterPlan();
         assertThat(plan.plan(), equalTo(request.remoteClusterPlan().plan()));
         assertThat(plan.targetIndices(), equalTo(request.remoteClusterPlan().targetIndices()));