audio,ges,rtsp-server: Define GstObjectExt trait rename for docs
The generator does not read Gir.toml from dependencies, missing out on
trait renames like ObjectExt
turning into GstObjectExt(to prevent clashes with
glib's
ObjectExt). Renaming through
trait_nameis now taken into account in
girthanks to [1], but the renames still need to be availble to all crates referencing this type. Fortunately only
Gst.Object` is affected - other renamed traits are not extended in
any of the other crates.