Remove all harmony runtime flags which shipped in M51

test/mjsunit/es6/no-unicode-regexp-flag.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.
-
-// Before Unicode RegExps are shipped, we shouldn't have the 'unicode'
-// property on RegExp.prototype, or read it from 'flags'.
-// mjsunit/es6/regexp-flags tests that the property is there when the
-// flag is on.
-
-// Flags: --no-harmony-unicode-regexps
-
-'use strict';
-
-assertFalse(RegExp.prototype.hasOwnProperty('unicode'));
-
-// If we were going to be really strict, we could have a test like this,
-// with the assertTrue replaced by assertFalse, since flags shouldn't
-// Get the 'unicode' property. However, it is probably OK to omit this
-// detailed fix.
-var x = /a/;
-var y = false;
-Object.defineProperty(x, 'unicode', { get() { y = true; } });
-assertEquals("", x.flags);
-assertTrue(y);