avfilter/vf_hysteresis: Remove always-false format check

This filter uses ff_set_common_formats_from_list().

Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavfilter/vf_hysteresis.c

@@ -295,10 +295,6 @@ static int config_output(AVFilterLink *outlink)
     FFFrameSyncIn *in;
     int ret;
 
-    if (base->format != alt->format) {
-        av_log(ctx, AV_LOG_ERROR, "inputs must be of same pixel format\n");
-        return AVERROR(EINVAL);
-    }
     if (base->w != alt->w || base->h != alt->h) {
         av_log(ctx, AV_LOG_ERROR, "First input link %s parameters "
                "(size %dx%d) do not match the corresponding "