Revert of Add content type information to encoded images and corresponding rtp extension header

webrtc/api/video/video_content_type.h

-/*
- *  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.
- */
-
-#ifndef WEBRTC_API_VIDEO_VIDEO_CONTENT_TYPE_H_
-#define WEBRTC_API_VIDEO_VIDEO_CONTENT_TYPE_H_
-
-#include <stdint.h>
-
-namespace webrtc {
-
-enum class VideoContentType : uint8_t {
-  UNSPECIFIED = 0,
-  SCREENSHARE = 1,
-  TOTAL_CONTENT_TYPES  // Must be the last value in the enum.
-};
-
-}  // namespace webrtc
-
-#endif  // WEBRTC_API_VIDEO_VIDEO_CONTENT_TYPE_H_