Fix compilation error

Author: kderusso

x-pack/plugin/search-business-rules/src/main/java/org/elasticsearch/xpack/searchbusinessrules/SearchBusinessRulesFeatures.java

@@ -12,6 +12,8 @@
 
 import java.util.Set;
 
+import static org.elasticsearch.xpack.searchbusinessrules.retriever.PinnedRetrieverBuilder.PINNED_RETRIEVER_FEATURE;
+
 public class SearchBusinessRulesFeatures implements FeatureSpecification {
 
     @Override