interleave: Remove unsed field
interleave: Remove unsed field

Remove unused field collect_event in interleave.

https://bugzilla.gnome.org/show_bug.cgi?id=759226

GrokImageCompression/gst-plugins-good,hizukiayaka/gst-plugins-good,pexip/gst-plugins-good,hizukiayaka/gst-plugins-good,StreamUtils/gst-plugins-good,GStreamer/gst-plugins-good,GrokImageCompression/gst-plugins-good,StreamUtils/gst-plugins-good,pexip/gst-plugins-good,stfl/gst-plugins-good,GrokImageCompression/gst-plugins-good,GStreamer/gst-plugins-good,stfl/gst-plugins-good,pexip/gst-plugins-good,GStreamer/gst-plugins-good,pexip/gst-plugins-good,Kurento/gst-plugins-good,GrokImageCompression/gst-plugins-good,GStreamer/gst-plugins-good,Kurento/gst-plugins-good,pexip/gst-plugins-good,hizukiayaka/gst-plugins-good,Kurento/gst-plugins-good,stfl/gst-plugins-good,StreamUtils/gst-plugins-good,stfl/gst-plugins-good,hizukiayaka/gst-plugins-good,Kurento/gst-plugins-good,StreamUtils/gst-plugins-good,Kurento/gst-plugins-good