Fix ConcurrentTransactionsTest failure with CockroachDB (#13890)

- realm has to be removed in a separate tx due to CRDB's SERIALIZABLE isolation level

Closes #13211

testsuite/integration-arquillian/tests/base/src/test/java/org/keycloak/testsuite/model/ConcurrentTransactionsTest.java

@@ -189,7 +189,7 @@ public class ConcurrentTransactionsTest extends AbstractTestRealmKeycloakTest {
 
             });
         } finally {
-            tearDownRealm(session, "user1", "user2");
+            KeycloakModelUtils.runJobInTransaction(session.getKeycloakSessionFactory(), kcSession -> tearDownRealm(kcSession, "user1", "user2"));
         }
     }