ffmpeg: remove dead code out of the video filter loop

It makes no sense for this code to be inside the video filter loop, and
the frame sample aspect ratio is even set unconditionally a few lines
above.

ffmpeg.c

@@ -2201,7 +2201,6 @@ static int decode_video(InputStream *ist, AVPacket *pkt, int *got_output, int eo
     int i, ret = 0, err = 0, resample_changed;
     int64_t best_effort_timestamp;
     int64_t dts = AV_NOPTS_VALUE;
-    AVRational *frame_sample_aspect;
     AVPacket avpkt;
 
     // With fate-indeo3-2, we're getting 0-sized packets before EOF for some
@@ -2347,11 +2346,7 @@ static int decode_video(InputStream *ist, AVPacket *pkt, int *got_output, int eo
         }
     }
 
-    frame_sample_aspect= av_opt_ptr(avcodec_get_frame_class(), decoded_frame, "sample_aspect_ratio");
     for (i = 0; i < ist->nb_filters; i++) {
-        if (!frame_sample_aspect->num)
-            *frame_sample_aspect = ist->st->sample_aspect_ratio;
-
         if (i < ist->nb_filters - 1) {
             f = ist->filter_frame;
             err = av_frame_ref(f, decoded_frame);