tests: Re-enable the nested object generator unit
tests: Re-enable the nested object generator unit

Use the JSON object example inside the RFC 4627 to verify that the
JsonGenerator creates the right output. This is now possible as we
garantee the order of a JsonObject members.

robtaylor/json-glib-gvariant,brauliobo/json-glib,Distrotech/json-glib,frida/json-glib,oerdnj/json-glib,oerdnj/json-glib,brauliobo/json-glib,oerdnj/json-glib,frida/json-glib,GNOME/json-glib,Distrotech/json-glib,robtaylor/json-glib-gvariant,ebassi/json-glib,brauliobo/json-glib,oerdnj/json-glib,GNOME/json-glib,ebassi/json-glib,Distrotech/json-glib,ebassi/json-glib