Do not transmit MediaCodec flags

Since PTS handling has been fixed, the recorder do not associate a PTS
to a wrong frame anymore, so PTS of "configuration packets" (which never
produce a frame), are never read by the recorder. Therefore, there is no
need to ignore them explicitly, so we can remove the MediaCodec flags
completely.

app/src/decoder.h

@@ -17,7 +17,6 @@ struct decoder {
     struct recorder *recorder;
     uint64_t next_pts;
     uint64_t pts;
-    uint32_t buffer_info_flags;
     int remaining;
 };