Remove temporary fix for drawing check box in the wxPG edit mode with RTL layout

Since the issue is fixed (r77020) this hack is no longer necessary (see #16254).

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@77025 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775