Remove references to mac valgrind bot.

PRESUBMIT_test.py

 #!/usr/bin/env python
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import re
 import subprocess
 import unittest
 
 import PRESUBMIT
@@ skipping 701 matching lines @@
             'ios_rel_device_ninja',
             'mac_asan',
             'mac_asan_64',
             'mac_chromium_compile_dbg',
             'mac_chromium_compile_rel',
             'mac_chromium_dbg',
             'mac_chromium_rel',
             'mac_nacl_sdk',
             'mac_nacl_sdk_build',
             'mac_rel_naclmore',
-            'mac_valgrind',
             'mac_x64_rel',
             'mac_xcodebuild',
         ],
         'tryserver.chromium.linux': [
             'android_aosp',
             'android_chromium_gn_compile_dbg',
             'android_chromium_gn_compile_rel',
             'android_clang_dbg',
             'android_dbg',
             'android_dbg_recipe',
@@ skipping 345 matching lines @@
                ['char* host = "https://www.aol.com"; // google.com'])
     ]
 
     warnings = PRESUBMIT._CheckHardcodedGoogleHostsInLowerLayers(
       input_api, MockOutputApi())
     self.assertEqual(0, len(warnings))
 
 
 if __name__ == '__main__':
   unittest.main()