This variable seemed to be redundant with m_requestedSashPosition being set to
INT_MAX so harmonise the code to always check for the latter and get rid of
the former.
There should be no observable changes in behaviour.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@69597 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775