lavf/gifdec: do not mark as notimestamps

The demuxer does not set packet timestamps itself after
c6b6356635f598b095606cd126f31bc6ab916225 and instead relies on the
parser to do it. However, this does not matter from the caller
perspective as it still happens inside the demuxer. The demuxer should
thus not be flagged as not having timestamps.

libavformat/gifdec.c

@@ -285,7 +285,7 @@ const AVInputFormat ff_gif_demuxer = {
     .read_probe     = gif_probe,
     .read_header    = gif_read_header,
     .read_packet    = gif_read_packet,
-    .flags          = AVFMT_GENERIC_INDEX | AVFMT_NOTIMESTAMPS,
+    .flags          = AVFMT_GENERIC_INDEX,
     .extensions     = "gif",
     .priv_class     = &demuxer_class,
 };