Cleaned up an unused variable

lib/util.js

@@ -1139,7 +1139,6 @@ exports.mergeOptions = function (mergeTarget, options, option) {
  */
 exports.binarySearch = function(orderedItems, range, field, field2) {
   var array = orderedItems;
-  var interval = range.end - range.start;
 
   var found = false;
   var low = 0;