Integer indexed property descriptor must be non-configurable (#786)

* Integer indexed property descriptor must be non-configurable

* Make the configurable key explicitly 'false'

test/built-ins/TypedArrays/internals/DefineOwnProperty/key-is-lower-than-zero.js

@@ -24,7 +24,7 @@ testWithTypedArrayConstructors(function(TA) {
   assert.sameValue(
     Reflect.defineProperty(sample, "-1", {
       value: 42,
-      configurable: true,
+      configurable: false,
       enumerable: true,
       writable: true
     }),