lavfi/vf_mpdecimate: remove request_frame().

It is no longer needed since looping is not necessary.

libavfilter/vf_mpdecimate.c

@@ -224,19 +224,6 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *cur)
     return 0;
 }
 
-static int request_frame(AVFilterLink *outlink)
-{
-    DecimateContext *decimate = outlink->src->priv;
-    AVFilterLink *inlink = outlink->src->inputs[0];
-    int ret;
-
-    do {
-        ret = ff_request_frame(inlink);
-    } while (decimate->drop_count > 0 && ret >= 0);
-
-    return ret;
-}
-
 static const AVFilterPad mpdecimate_inputs[] = {
     {
         .name         = "default",
@@ -251,7 +238,6 @@ static const AVFilterPad mpdecimate_outputs[] = {
     {
         .name          = "default",
         .type          = AVMEDIA_TYPE_VIDEO,
-        .request_frame = request_frame,
     },
     { NULL }
 };