amix: fix format specifier for AVFilterLink.sample_rate.

It is a plain int now.

libavfilter/af_amix.c

@@ -261,7 +261,7 @@ static int config_output(AVFilterLink *outlink)
     av_get_channel_layout_string(buf, sizeof(buf), -1, outlink->channel_layout);
 
     av_log(ctx, AV_LOG_VERBOSE,
-           "inputs:%d fmt:%s srate:%"PRId64" cl:%s\n", s->nb_inputs,
+           "inputs:%d fmt:%s srate:%d cl:%s\n", s->nb_inputs,
            av_get_sample_fmt_name(outlink->format), outlink->sample_rate, buf);
 
     return 0;