Lower version on full cluster restart settings test

The change to upgrade cross-cluster search settings was backported to
6.5.0. Therefore, this assumption needs to be reduced to the latest
version where settings were not automatically upgraded.

qa/full-cluster-restart/src/test/java/org/elasticsearch/upgrades/FullClusterRestartSettingsUpgradeIT.java

@@ -42,7 +42,7 @@ import static org.hamcrest.Matchers.equalTo;
 public class FullClusterRestartSettingsUpgradeIT extends AbstractFullClusterRestartTestCase {
 
     public void testRemoteClusterSettingsUpgraded() throws IOException {
-        assumeTrue("settings automatically upgraded since 7.0.0", getOldClusterVersion().before(Version.V_7_0_0_alpha1));
+        assumeTrue("settings automatically upgraded since 6.5.0", getOldClusterVersion().before(Version.V_6_5_0));
         if (isRunningAgainstOldCluster()) {
             final Request putSettingsRequest = new Request("PUT", "/_cluster/settings");
             try (XContentBuilder builder = jsonBuilder()) {