Fix build issue

Author: Ganeshwara Hananda

common/Printer.java

@@ -77,7 +77,7 @@ private String conceptMapDisplayString(ConceptMap conceptMap, Grakn.Transaction
         StringBuilder sb = new StringBuilder();
         sb.append("{ ");
         for (Map.Entry<String, Concept> entry : conceptMap.map().entrySet()) {
-            Reference.Name variable = Reference.named(entry.getKey());
+            Reference.Name variable = Reference.name(entry.getKey());
             Concept concept = entry.getValue();
             sb.append(variable.syntax());
             sb.append(" ");