Remove unneeded keyword check.

Special keywords are handled before this point.

Author: davidlehn

lib/expand.js

@@ -762,12 +762,9 @@ async function _expandObject({
     }
 
     // add value for property
-    // use an array except for certain keywords
-    const useArray =
-      !['@index', '@id', '@type', '@value', '@language']
-        .includes(expandedProperty);
+    // special keywords handled above
     _addValue(expandedParent, expandedProperty, expandedValue, {
-      propertyIsArray: useArray
+      propertyIsArray: true
     });
   }