MB: Remove unnecessary configs.

webrtc/build/mb_config.pyl

 # Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 # FOR DETAILS ON THIS FILE SEE THE MAIN COPY IN //tools/mb/mb_config.pyl.
 # This is configuration for standalone WebRTC bots. It is used to keep the bot
@@ skipping 110 matching lines @@
       'ios_dbg': 'ios_gyp_debug_bot_arm_device',
       'ios_rel': 'ios_gyp_release_bot_arm_device',
       'ios_arm64_dbg': 'ios_gyp_debug_bot_arm64_device',
       'ios_arm64_rel': 'ios_gyp_release_bot_arm64_device',
       'ios32_sim_dbg': 'ios_gyp_debug_bot_x86',
       'ios64_sim_dbg': 'ios_gyp_debug_bot_x64',
       'ios64_gn_dbg': 'ios_gn_debug_bot_arm64_device',
       'ios64_gn_rel': 'ios_gn_release_bot_arm64_device',
     },
   },
-
-  # These lists are assumed to exist so we need them in order to be able to run
-  # the mb.py script in PRESUBMIT.py to verify our config is sane.
-  'common_dev_configs': [],
-  'private_configs': [],
-  'unsupported_configs': [],
 }