testShrinkAfterUpgrade should only set mapping.single_type if bwc version > 5.5.0

It was only added in #24317

Author: bleskes

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

@@ -430,7 +430,10 @@ public void testShrinkAfterUpgrade() throws IOException {
         if (runningAgainstOldCluster) {
             XContentBuilder mappingsAndSettings = jsonBuilder();
             mappingsAndSettings.startObject();
-            if (oldClusterVersion.major == 5 && randomBoolean()) {
+            // single type was added in 5.5.0 (see #24317)
+            if (oldClusterVersion.onOrAfter(Version.V_5_5_0) &&
+                oldClusterVersion.before(Version.V_6_0_0_beta1) &&
+                randomBoolean()) {
                 {
                     // test that mapping.single_type is correctly propagated on the shrinked index,
                     // if not, search will fail.