json-glib: Remove unused symbols
json-glib: Remove unused symbols

Or compilation fails with -Werror

https://bugzilla.gnome.org/show_bug.cgi?id=773604

ebassi/json-glib,ebassi/json-glib,ebassi/json-glib,frida/json-glib,GNOME/json-glib,frida/json-glib,GNOME/json-glib