[Test] Fix failing RBACEngineTests (elastic#126106)

Adjusting the test assertion to account for the potential 3rd extra
group (elastic#125900).

Resolves elastic#126061

Author: slobodanadamovic

muted-tests.yml

@@ -389,9 +389,6 @@ tests:
 - class: org.elasticsearch.action.RejectionActionIT
   method: testSimulatedSearchRejectionLoad
   issue: https://github.com/elastic/elasticsearch/issues/125901
-- class: org.elasticsearch.xpack.security.authz.RBACEngineTests
-  method: testGetRoleDescriptorsIntersectionForRemoteClusterHasDeterministicOrderForIndicesPrivileges
-  issue: https://github.com/elastic/elasticsearch/issues/126061
 - class: org.elasticsearch.search.CCSDuelIT
   method: testTerminateAfter
   issue: https://github.com/elastic/elasticsearch/issues/126085

x-pack/plugin/security/src/test/java/org/elasticsearch/xpack/security/authz/RBACEngineTests.java

@@ -1699,10 +1699,10 @@ public void testGetRoleDescriptorsIntersectionForRemoteClusterHasDeterministicOr
             Set<IndexPrivilege> splitBySelector = IndexPrivilege.resolveBySelectorAccess(
                 Set.copyOf(randomSubsetOf(randomIntBetween(1, 4), IndexPrivilege.names()))
             );
-            // If we end up with failure and data access, we will split and end up with extra groups. Need to account for this for the
-            // final assertion
-            if (splitBySelector.size() == 2) {
-                extraGroups++;
+            // If we end up with failure and data access (or failure, data and failure and data access),
+            // we will split and end up with extra groups. Need to account for this for the final assertion
+            if (splitBySelector.size() >= 2) {
+                extraGroups += splitBySelector.size() - 1;
             }
             for (var privilege : splitBySelector) {
                 remoteIndicesBuilder.addGroup(