Remove `whitespace_around_ops` pending re-name and re-design (#249).

test/rules/whitespace_around_ops.dart

-// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-// test w/ `dart test/util/solo_test.dart whitespace_around_ops`
-
-
-// Define our own int so we don't need `int` in our mock SDK.
-class MyInt {
-  MyInt operator -() => this;
-  MyInt operator ~() => this;
-  MyInt operator ~/(MyInt other) => this;
-  MyInt operator /(MyInt other) => this;
-}
-
-void main() {
-  MyInt f, g;
-  print(f ~/ g);
-  print(f~/ g); //LINT
-  print(f ~/g); //LINT
-  print(f~/g); //LINT
-  print(f/ ~g); //LINT
-  print(f /~g); //LINT
-  print(f / ~g); //OK
-  f =- g; //LINT
-  f = -g; //OK
-}