DATAES-405 - use org.springframework.lang.Nullable.

Original PR: spring-projects#300

Author: sothawo

src/main/java/org/springframework/data/elasticsearch/client/util/RequestConverters.java

@@ -61,7 +61,6 @@
 import org.elasticsearch.client.Requests;
 import org.elasticsearch.client.RethrottleRequest;
 import org.elasticsearch.cluster.health.ClusterHealthStatus;
-import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.Priority;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.SuppressForbidden;
@@ -86,6 +85,7 @@
 import org.elasticsearch.tasks.TaskId;
 import org.springframework.data.elasticsearch.client.reactive.ReactiveElasticsearchClient;
 import org.springframework.http.HttpMethod;
+import org.springframework.lang.Nullable;
 
 /**
  * <p>

src/main/java/org/springframework/data/elasticsearch/core/query/BulkOptions.java

@@ -19,8 +19,8 @@
 
 import org.elasticsearch.action.support.ActiveShardCount;
 import org.elasticsearch.action.support.WriteRequest;
-import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.unit.TimeValue;
+import org.springframework.lang.Nullable;
 
 /**
  * Options that may be passed to an