Missing doc blurbs for pbutils Encoding Targets in hotdoc

With gtk-doc there's a blurb about encoding targets, describing the keyfile like files, etc; this appears missing from the official hotdoc code.

Basically the chunk around

 * ## Encoding target serialization format
 *
 * Encoding targets are serialized in a KeyFile like files.

It's there with gtk-doc in devhelp, and interestingly also this hotdoc version: https://thiblahute.github.io/GStreamer-doc/gst-plugins-base-pbutils-1.0/encoding-target.html?gi-language=c

But is missing from the official docs: https://gstreamer.freedesktop.org/documentation/pbutils/encoding-target.html?gi-language=c