Revert "Android: Generate JNI code for VideoSink and VideoEncoder"

This reverts commit ba78b5a905bffa05933a135673996df02328f2a4.

Reason for revert: Breaks external projects.

Original change's description:
> Android: Generate JNI code for VideoSink and VideoEncoder
> 
> This is the first CL to start generating JNI code. It has updated two of
> the most recent classes to use JNI code generation.
> 
> Bug: webrtc:8278
> Change-Id: I1b19ee78c273346ceeaa0401dbdf8696803f16c7
> Reviewed-on: https://webrtc-review.googlesource.com/3820
> Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
> Commit-Queue: Magnus Jedvert <magjed@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#19994}

TBR=magjed@webrtc.org,sakal@webrtc.org

Change-Id: I48e079f3ab9661ae4171a3ae5cca571a75d14810
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:8278
Reviewed-on: https://webrtc-review.googlesource.com/4100
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Commit-Queue: Magnus Jedvert <magjed@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#19997}

sdk/android/api/org/webrtc/VideoSink.java

@@ -19,5 +19,5 @@ public interface VideoSink {
    * this function returns. Each call to retain() should be followed by a call to frame.release()
    * when the reference is no longer needed.
    */
-  @CalledByNative void onFrame(VideoFrame frame);
+  void onFrame(VideoFrame frame);
 }