Reenable test after backport

This commit re-enables CCR rolling upgrade tests following the
backport of elastic#58217 to 7.8 branch (7.8.1)

Author: tvernum

x-pack/qa/rolling-upgrade-multi-cluster/src/test/java/org/elasticsearch/upgrades/CcrRollingUpgradeIT.java

@@ -13,7 +13,6 @@
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.xcontent.ObjectPath;
 import org.elasticsearch.common.xcontent.support.XContentMapValues;
-import org.junit.Before;
 
 import java.io.IOException;
 import java.util.Map;
@@ -24,11 +23,6 @@
 
 public class CcrRollingUpgradeIT extends AbstractMultiClusterUpgradeTestCase {
 
-    @Before
-    public void skipForBackportOf58217() {
-        assumeFalse("Skip while back-porting #58217", UPGRADE_FROM_VERSION.equals(Version.V_7_8_1));
-    }
-
     public void testUniDirectionalIndexFollowing() throws Exception {
         logger.info("clusterName={}, upgradeState={}", clusterName, upgradeState);