don't use string module

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73603 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Minor tweaks to the preferences docs for Phoenix.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73604 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775