avfilter/vf_zoompan: remove AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC

Suggested-by: <durandal_1707>
Fixes: assertion failure
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavfilter/vf_zoompan.c

@@ -373,5 +373,4 @@ AVFilter ff_vf_zoompan = {
     .activate      = activate,
     .inputs        = inputs,
     .outputs       = outputs,
-    .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC,
 };