Remove client.type setting (#118192)

The client.type setting is a holdover from the node client which was
removed in 8.0. The setting has been a noop since 8.0. This commit
removes the setting.

relates #104574

docs/changelog/118192.yaml

@@ -0,0 +1,11 @@
+pr: 118192
+summary: Remove `client.type` setting
+area: Infra/Core
+type: breaking
+issues: [104574]
+breaking:
+  title: Remove `client.type` setting
+  area: Cluster and node setting
+  details: The node setting `client.type` has been ignored since the node client was removed in 8.0. The setting is now removed.
+  impact: Remove the `client.type` setting from `elasticsearch.yml` 
+  notable: false

server/src/main/java/org/elasticsearch/client/internal/Client.java

@@ -52,8 +52,6 @@
 import org.elasticsearch.action.update.UpdateRequest;
 import org.elasticsearch.action.update.UpdateRequestBuilder;
 import org.elasticsearch.action.update.UpdateResponse;
-import org.elasticsearch.common.settings.Setting;
-import org.elasticsearch.common.settings.Setting.Property;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.core.Nullable;
 import org.elasticsearch.transport.RemoteClusterService;
@@ -74,14 +72,6 @@
  */
 public interface Client extends ElasticsearchClient {
 
-    // Note: This setting is registered only for bwc. The value is never read.
-    Setting<String> CLIENT_TYPE_SETTING_S = new Setting<>("client.type", "node", (s) -> {
-        return switch (s) {
-            case "node", "transport" -> s;
-            default -> throw new IllegalArgumentException("Can't parse [client.type] must be one of [node, transport]");
-        };
-    }, Property.NodeScope, Property.Deprecated);
-
     /**
      * The admin client that can be used to perform administrative operations.
      */

server/src/main/java/org/elasticsearch/common/settings/ClusterSettings.java

@@ -20,7 +20,6 @@
 import org.elasticsearch.action.support.DestructiveOperations;
 import org.elasticsearch.action.support.replication.TransportReplicationAction;
 import org.elasticsearch.bootstrap.BootstrapSettings;
-import org.elasticsearch.client.internal.Client;
 import org.elasticsearch.cluster.ClusterModule;
 import org.elasticsearch.cluster.ClusterName;
 import org.elasticsearch.cluster.InternalClusterInfoService;
@@ -483,7 +482,6 @@ public void apply(Settings value, Settings current, Settings previous) {
         AutoCreateIndex.AUTO_CREATE_INDEX_SETTING,
         BaseRestHandler.MULTI_ALLOW_EXPLICIT_INDEX,
         ClusterName.CLUSTER_NAME_SETTING,
-        Client.CLIENT_TYPE_SETTING_S,
         ClusterModule.SHARDS_ALLOCATOR_TYPE_SETTING,
         EsExecutors.NODE_PROCESSORS_SETTING,
         ThreadContext.DEFAULT_HEADERS_SETTING,