wxGUI/toolboxes: fix link (lower case letters preferred)

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@57004 15284696-431f-4ddb-bdfa-cd5b030d7da7

gui/wxpython/docs/wxGUI.html

@@ -631,7 +631,7 @@ the computational region extents.
 
 <em>
   <a href="wxGUI.Components.html">wxGUI components</a><br/>
-  <a href="wxGUI.Toolboxes.html">wxGUI toolboxes (menu customization)</a>
+  <a href="wxGUI.toolboxes.html">wxGUI toolboxes (menu customization)</a>
 </em>
 
 <p>