EVT_TREE_STATE_IMAGE_CLICK is not Windows-only any more.

State images in wxTreeCtrl are now supported under all platforms.

See #9591.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73824 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775