Remove DartSQLTransactionSyncCustom dpesn't seem to be used in V8 anymore and we don't seem to gene…

Source/bindings/modules/dart/custom/custom.gypi

 # Copyright 2014 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': {
         'bindings_modules_dart_custom_files': [
             'DartAudioContextCustom.cpp',
             'DartAudioNodeCustom.cpp',
             'DartAudioParamCustom.cpp',
             'DartBiquadFilterNodeCustom.cpp',
             'DartCryptoCustom.cpp',
             'DartCryptoKeyCustom.cpp',
             'DartDeviceMotionEventCustom.cpp',
             'DartDeviceOrientationEventCustom.cpp',
             'DartEntryCustom.cpp',
             'DartEntrySyncCustom.cpp',
             'DartOscillatorNodeCustom.cpp',
             'DartSQLResultSetRowListCustom.cpp',
             'DartSQLStatementErrorCallbackCustom.cpp',
             'DartSQLTransactionCustom.cpp',
-            'DartSQLTransactionSyncCustom.cpp',
             'DartScriptProcessorNodeCustom.cpp',
             'DartServiceWorkerClientCustom.cpp',
             'DartServiceWorkerCustom.cpp',
             'DartSubtleCryptoCustom.cpp',
             'DartWaveShaperNodeCustom.cpp',
         ],
     },
 }