livesync: log new pending segments

The debug print of the event does not display details about the segment:
  Unqueueing Some(Event(Event { ptr: 0x7fa3e0002580, type: "segment", seqnum: Seqnum(479), structure: Some(GstEventSegment { segment: (GstSegment) ((GstSegment*) 0x7fa3e8001d00) }) }))

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/1387>

utils/livesync/src/livesync/imp.rs

@@ -1063,6 +1063,7 @@ impl LiveSync {
                 match event.view() {
                     gst::EventView::Segment(e) => {
                         let segment = e.segment().downcast_ref().unwrap();
+                        gst::debug!(CAT, imp: self, "pending {segment:?}");
                         state.pending_segment = Some(segment.clone());
                         push = false;
                     }