Remove unused variable.

lodash.js

@@ -1473,7 +1473,6 @@
         getPrototype = overArg(Object.getPrototypeOf, Object),
         iteratorSymbol = Symbol ? Symbol.iterator : undefined,
         objectCreate = Object.create,
-        propertyIsEnumerable = objectProto.propertyIsEnumerable,
         splice = arrayProto.splice,
         spreadableSymbol = Symbol ? Symbol.isConcatSpreadable : undefined;