transcode: keep original timestamp in audio and not calculated pts

Allow audio pts fluctuate within drift limits as we calculate the drift
related to master sync time anyway.

modules/stream_out/transcode/audio.c

@@ -222,7 +222,6 @@ int transcode_audio_process( sout_stream_t *p_stream,
             if( likely(p_audio_buf->i_pts != VLC_TS_INVALID ) )
                 p_sys->i_master_drift = p_audio_buf->i_pts - i_pts;
             date_Increment( &id->interpolated_pts, p_audio_buf->i_nb_samples );
-            p_audio_buf->i_pts = i_pts;
         }
 
         p_audio_buf->i_dts = p_audio_buf->i_pts;