Remove runtime flags for Proxy and Reflect

test/mjsunit/es6/tail-call-proxies.js

 // Copyright 2016 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: --allow-natives-syntax --harmony-tailcalls --harmony-proxies
+// Flags: --allow-natives-syntax --harmony-tailcalls
 "use strict";
 
 Error.prepareStackTrace = (e,s) => s;
 
 function CheckStackTrace(expected) {
   var stack = (new Error()).stack;
   assertEquals("CheckStackTrace", stack[0].getFunctionName());
   for (var i = 0; i < expected.length; i++) {
     assertEquals(expected[i].name, stack[i + 1].getFunctionName());
   }
@@ skipping 72 matching lines @@
 
   // Callee has arguments adaptor frame.
   function f4(a, b, c) {
     CheckStackTrace([f4, test]);
     return 10 + a;
   }
   var p4 = new Proxy(f4, {});
   function g4(a) { return p4(2); }
   assertEquals(12, g4());
 })();