Remove references to an old gyp variable that's no longer supported.

build/isolate.gypi

 # 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.
 
 # This file is meant to be included into a target to provide a rule
 # to "build" .isolate files into a .isolated file.
 #
 # To use this, create a gyp target with the following form:
 # 'conditions': [
 #   ['test_isolation_mode != "noop"', {
@@ skipping 71 matching lines @@
         '--config-variable', 'disable_nacl=<(disable_nacl)',
         '--config-variable', 'enable_pepper_cdms=<(enable_pepper_cdms)',
         '--config-variable', 'enable_plugins=<(enable_plugins)',
         '--config-variable', 'fastbuild=<(fastbuild)',
         '--config-variable', 'icu_use_data_file_flag=<(icu_use_data_file_flag)',
         # TODO(kbr): move this to chrome_tests.gypi:gles2_conform_tests_run
         # once support for user-defined config variables is added.
         '--config-variable',
           'internal_gles2_conform_tests=<(internal_gles2_conform_tests)',
         '--config-variable', 'kasko=<(kasko)',
-        '--config-variable', 'libpeer_target_type=<(libpeer_target_type)',
         '--config-variable', 'lsan=<(lsan)',
         '--config-variable', 'msan=<(msan)',
         '--config-variable', 'target_arch=<(target_arch)',
         '--config-variable', 'tsan=<(tsan)',
         '--config-variable', 'use_custom_libcxx=<(use_custom_libcxx)',
         '--config-variable', 'use_instrumented_libraries=<(use_instrumented_libraries)',
         '--config-variable',
         'use_prebuilt_instrumented_libraries=<(use_prebuilt_instrumented_libraries)',
         '--config-variable', 'use_openssl=<(use_openssl)',
         '--config-variable', 'use_ozone=<(use_ozone)',
@@ skipping 22 matching lines @@
           ],
         }, {
           'action': [
             '--config-variable', 'msvs_version=0',
           ],
         }],
       ],
     },
   ],
 }