Make Move{Before,After}InTabOrder() work at any time in wxGTK.

These functions only worked if called at the beginning, before showing the
parent window containing the children whose TAB order was being adjusted,
because it didn't refresh the GTK+ TAB order on the correct window: we need to
do it for the parent of the window being moved, not this window itself.

Closes #16032.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76101 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775