gobject-2.0: Fix the Closure.invoke() signature
gobject-2.0: Fix the Closure.invoke() signature

The return value must be initialized by the caller, as is clear from
GLib's internal callers, and e.g. dummy_closure_marshal() on the callee
side. So it appears the GLib type annotation is incorrect, as it
specifies `out` but should be `inout`.

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