media.MediaMuxer: remove unused SAMPLE_FLAG_SYNC flag.

This is not actually used, and introduces flag translation
code for all users of this new MediaMuxer API.

Change-Id: I8baa2b13d7e637142f6e3b18a170e6329b90bd5e
Signed-off-by: Lajos Molnar <lajos@google.com>
Bug: 9169479
diff --git a/api/18.txt b/api/18.txt
index a9d0f57..942cd57 100644
--- a/api/18.txt
+++ b/api/18.txt
@@ -11989,7 +11989,6 @@
     method public void start();
     method public void stop();
     method public void writeSampleData(int, java.nio.ByteBuffer, android.media.MediaCodec.BufferInfo);
-    field public static final int SAMPLE_FLAG_SYNC = 1; // 0x1
   }
 
   public static final class MediaMuxer.OutputFormat {