Make OTLP endpoint available on serverless (elastic#136153)

Author: felixbarny

x-pack/plugin/otel-data/src/main/java/org/elasticsearch/xpack/oteldata/otlp/OTLPMetricsRestAction.java

@@ -16,13 +16,16 @@
 import org.elasticsearch.rest.RestRequest;
 import org.elasticsearch.rest.RestResponse;
 import org.elasticsearch.rest.RestStatus;
+import org.elasticsearch.rest.Scope;
+import org.elasticsearch.rest.ServerlessScope;
 import org.elasticsearch.rest.action.RestResponseListener;
 
 import java.io.IOException;
 import java.util.List;
 
 import static org.elasticsearch.rest.RestRequest.Method.POST;
 
+@ServerlessScope(Scope.PUBLIC)
 public class OTLPMetricsRestAction extends BaseRestHandler {
     @Override
     public String getName() {