analysis/properties: Remove unused ToValue import for property getters
analysis/properties: Remove unused ToValue import for property getters

Following [1] an unnecessary `glib::ToValue` import showed up in auto
code, which does not appear to be used in gtk-rs nor gstreamer-rs.
After all, getters convert from Values, not to Values.

Fixes: c6cacb0 ("Implement handling of new Value traits")

[1]: https://gitlab.freedesktop.org/gstreamer/gstreamer-rs/-/merge_requests/746#note_893561

gtk-rs/gir,GuillaumeGomez/gir,gtk-rs/gir,GuillaumeGomez/gir,GuillaumeGomez/gir,gtk-rs/gir