remove libwebm third_party dependency

remoting/client/BUILD.gn

 # 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.
 
 import("//remoting/remoting_version.gni")
 
 static_library("client") {
   gypi_values = exec_script("//build/gypi_to_gn.py",
                             [ rebase_path("../remoting_srcs.gypi") ],
                             "scope",
                             [ "../remoting_srcs.gypi" ])
 
   sources = rebase_path(gypi_values.remoting_client_sources, ".", "//remoting")
 
   configs += [ "//build/config/compiler:wexit_time_destructors" ]
 
   defines = [ "VERSION=$version_full" ]
 
   deps = [
     "//remoting/base",
     "//remoting/protocol",
     "//third_party/libyuv",
     "//third_party/webrtc/modules/desktop_capture",
-    "//third_party/libwebm",
   ]
 }