codegen: Fix GDestroyNotify of delegate parameters in delegate declaration
codegen: Fix GDestroyNotify of delegate parameters in delegate declaration

delegate void Func (owned Func func);

incompatible pointer type: expected ‘void (**)(void *)’ but argument is
of type ‘GDestroyNotify {aka void (*)(void *)}’

https://bugzilla.gnome.org/show_bug.cgi?id=639059

GNOME/vala,frida/vala,GNOME/vala,frida/vala,frida/vala,GNOME/vala,GNOME/vala,frida/vala,frida/vala