Update cast certificate OWNERS list.

WATCHLISTS

 # 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.
 
 # Watchlist Rules
 # Refer: http://dev.chromium.org/developers/contributing-code/watchlists
 
 # IMPORTANT: The regular expression filepath is tested against each path using
 # re.search, so it is not usually necessary to add .*.
 
@@ skipping 1742 matching lines @@
                'rouslan+bubble@chromium.org'],
     'cache_storage': ['jkarlin+watch@chromium.org',
                       'nhiroki@chromium.org'],
     'cast': ['avayvod+watch@chromium.org',
              'imcheng+watch@chromium.org',
              'isheriff+watch@chromium.org',
              'jasonroberts+watch@google.com',
              'miu+watch@chromium.org',
              'xjz+watch@chromium.org'],
     'cast_certificate': ['dougsteed+watch@chromium.org',
-                         'ryanchung+watch@chromium.org',
-                         'sheretov+watch@chromium.org',
-                         'vadimgo+watch@chromium.org'],
+                         'ryanchung+watch@chromium.org'],
     'cc': ['cc-bugs@chromium.org'],
     'certificate_transparency': ['certificate-transparency-chrome@googlegroups.com',
                                  'eranm@chromium.org',
                                  'martijn+crwatch@martijnc.be',
                                  'rsleevi+watch@chromium.org'],
     'chrome_elf': ['caitkp+watch@chromium.org',
                    'pennymac+watch@chromium.org'],
     'chrome_views': ['tfarina@chromium.org'],
     'chromecast': ['alokp+watch@chromium.org',
                    'halliwell+watch@chromium.org',
@@ skipping 315 matching lines @@
                          'raymes+watch@chromium.org'],
     'windows_sandboxing': ['pennymac+watch@chromium.org',
                            'wfh+watch@chromium.org'],
     'x11': ['derat+watch@chromium.org',
             'sadrul@chromium.org',
             'yusukes+watch@chromium.org'],
     'xml': ['dominicc+watchlist@chromium.org'],
     'zoom': ['wjmaclean@chromium.org'],
   },
 }