Remove InsecureContentInfobarDelegate, which has been broken for a while

chrome/chrome_browser.gypi

 # Copyright 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.
 
 {
   'variables': {
     # All .cc, .h, .m, and .mm files under browser except for:
     # * tests and mocks.
     # * code below browser/chromeos
     # * code below browser/extensions
@@ skipping 271 matching lines @@
       'browser/icon_manager.cc',
       'browser/icon_manager.h',
       'browser/image_decoder.cc',
       'browser/image_decoder.h',
       'browser/image_holder.cc',
       'browser/image_holder.h',
       'browser/infobars/infobar_responder.cc',
       'browser/infobars/infobar_responder.h',
       'browser/infobars/infobar_service.cc',
       'browser/infobars/infobar_service.h',
-      'browser/infobars/insecure_content_infobar_delegate.cc',
-      'browser/infobars/insecure_content_infobar_delegate.h',
       'browser/install_verification/win/install_verification.cc',
       'browser/install_verification/win/install_verification.h',
       'browser/install_verification/win/loaded_module_verification.cc',
       'browser/install_verification/win/loaded_module_verification.h',
       'browser/install_verification/win/module_ids.cc',
       'browser/install_verification/win/module_ids.h',
       'browser/install_verification/win/module_info.h',
       'browser/install_verification/win/module_list.cc',
       'browser/install_verification/win/module_list.h',
       'browser/install_verification/win/module_verification_common.cc',
@@ skipping 4034 matching lines @@
             '../components/components.gyp:rlz',
             '../components/components.gyp:search_engines',
             '../rlz/rlz.gyp:rlz_lib',
             'common',
           ],
         },
       ],
     }],
   ],
 }