Revert of Opus implementation of the AudioEncoderFactoryTemplate API

webrtc/api/audio_codecs/opus/BUILD.gn

-# Copyright (c) 2017 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.
-
-import("../../../webrtc.gni")
-if (is_android) {
-  import("//build/config/android/config.gni")
-  import("//build/config/android/rules.gni")
-}
-
-rtc_static_library("audio_encoder_opus_config") {
-  sources = [
-    "audio_encoder_opus_config.cc",
-    "audio_encoder_opus_config.h",
-  ]
-  deps = [
-    "../../../base:rtc_base_approved",
-  ]
-  defines = []
-  if (rtc_opus_variable_complexity) {
-    defines += [ "WEBRTC_OPUS_VARIABLE_COMPLEXITY=1" ]
-  } else {
-    defines += [ "WEBRTC_OPUS_VARIABLE_COMPLEXITY=0" ]
-  }
-}
-
-rtc_static_library("audio_encoder_opus") {
-  sources = [
-    "audio_encoder_opus.cc",
-    "audio_encoder_opus.h",
-  ]
-  deps = [
-    ":audio_encoder_opus_config",
-    "..:audio_codecs_api",
-    "../../../base:protobuf_utils",  # TODO(kwiberg): Why is this needed?
-    "../../../base:rtc_base_approved",
-    "../../../modules/audio_coding:webrtc_opus",
-  ]
-}