Remove effectful assertion

test/mjsunit/harmony/regress/regress-crbug-461520.js

+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --harmony-proxies
+
+var fuse = 1;
+var handler = {
+  get: function() { return function() {} },
+  getPropertyDescriptor: function() {
+    if (fuse-- == 0) throw "please die";
+    return {value: function() {}, configurable: true};
+  }
+};
+
+var p = Proxy.create(handler);
+var o = Object.create(p);
+with (o) { f() }