We don't really care if we use deprecated API inside deprecated code, so just ignore the warning.
This reverts commit 4a72563c7b. It turns out that this commit broke statusicons under Xfce when not using a compositor. https://bugzilla.gnome.org/show_bug.cgi?id=737986
4a72563c7b
GtkStatusIcon is using a problematic, XEmbed-based protocol under X, and we want to get rid of it eventually. Document our intentions by marking GtkStatusIcon as deprecated. https://bugzilla.gnome.org/show_bug.cgi?id=734826