Gnc-Prefs: migrate GtkCheckbutton widgets (and associated preferences) - last batch

All GtkCheckButtons now use the new preferences backend
so drop the GtkCheckButton-Gconf wiring as well.

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@23239 57a11ea4-9604-0410-9ed3-97b8803252fd