Remove UnknownNamedObjectException (elastic#53105)

This was originally thrown from NamedXContentRegistry#parseNamedObject() but
that method now throws a NamedObjectNotFoundException, so this is unused.

Author: romseygeek

server/src/main/java/org/elasticsearch/ElasticsearchException.java

@@ -1007,8 +1007,7 @@ private enum ElasticsearchExceptionHandle {
             org.elasticsearch.tasks.TaskCancelledException::new, 146, UNKNOWN_VERSION_ADDED),
         SHARD_LOCK_OBTAIN_FAILED_EXCEPTION(org.elasticsearch.env.ShardLockObtainFailedException.class,
                                            org.elasticsearch.env.ShardLockObtainFailedException::new, 147, UNKNOWN_VERSION_ADDED),
-        UNKNOWN_NAMED_OBJECT_EXCEPTION(org.elasticsearch.common.xcontent.UnknownNamedObjectException.class,
-                org.elasticsearch.common.xcontent.UnknownNamedObjectException::new, 148, UNKNOWN_VERSION_ADDED),
+        // 148 was UnknownNamedObjectException
         TOO_MANY_BUCKETS_EXCEPTION(MultiBucketConsumerService.TooManyBucketsException.class,
             MultiBucketConsumerService.TooManyBucketsException::new, 149, UNKNOWN_VERSION_ADDED),
         COORDINATION_STATE_REJECTED_EXCEPTION(org.elasticsearch.cluster.coordination.CoordinationStateRejectedException.class,

server/src/main/java/org/elasticsearch/common/xcontent/UnknownNamedObjectException.java

@@ -55,7 +55,6 @@
 import org.elasticsearch.common.unit.ByteSizeValue;
 import org.elasticsearch.common.util.CancellableThreadsTests;
 import org.elasticsearch.common.util.set.Sets;
-import org.elasticsearch.common.xcontent.UnknownNamedObjectException;
 import org.elasticsearch.common.xcontent.XContentLocation;
 import org.elasticsearch.env.ShardLockObtainFailedException;
 import org.elasticsearch.index.Index;
@@ -808,7 +807,7 @@ public void testIds() {
         ids.put(145, org.elasticsearch.ElasticsearchStatusException.class);
         ids.put(146, org.elasticsearch.tasks.TaskCancelledException.class);
         ids.put(147, org.elasticsearch.env.ShardLockObtainFailedException.class);
-        ids.put(148, UnknownNamedObjectException.class);
+        ids.put(148, null);
         ids.put(149, MultiBucketConsumerService.TooManyBucketsException.class);
         ids.put(150, CoordinationStateRejectedException.class);
         ids.put(151, SnapshotInProgressException.class);