Remove hard TABs from documentation files

No real changes.

interface/wx/listbox.h

@@ -62,8 +62,8 @@
     @event{EVT_LISTBOX_DCLICK(id, func)}
         Process a @c wxEVT_LISTBOX_DCLICK event, when the listbox
         is double-clicked. On some platforms (notably wxGTK2)
-	pressing the enter key is handled as an equivalent of a 
-	double-click.
+        pressing the enter key is handled as an equivalent of a
+        double-click.
     @endEventTable
 
     @library{wxcore}

interface/wx/log.h

@@ -801,7 +801,7 @@ public:
         The messages will be written in the encoding specified by the
         given @c wxMBConv.
 
-		The @a conv argument is only available in wxWidgets 3.1.1 and later.
+        The @a conv argument is only available in wxWidgets 3.1.1 and later.
 
         @note
             In practice, it is only advisable to specify @c wxConvUTF8 as