Remove documentation of wxPostDelete()

This function not only doesn't exist, but seems to never have existed at
all.

Not really sure what happened here, but we definitely don't need to
document it any more.

interface/wx/utils.h

@@ -653,20 +653,6 @@ char* wxLoadUserResource(const wxString& resourceName,
                          int* pLen = NULL,
                          WXHINSTANCE module = 0);
 
-/**
-    @deprecated Replaced by wxWindow::Close(). See the
-                @ref overview_windowdeletion "window deletion overview".
-
-    Tells the system to delete the specified object when all other events have
-    been processed. In some environments, it is necessary to use this instead
-    of deleting a frame directly with the delete operator, because some GUIs
-    will still send events to a deleted window.
-
-    @header{wx/utils.h}
-*/
-void wxPostDelete(wxObject* object);
-
-
 /**
     Compare function type for use with wxQsort()