gf-tutorial: fix link to JavaScript translator demo

After fixing trivial problem in translator.html, the demo works, but
the example grammar contains only one langauge, so it is not so
interesting. translator.html is located in src/runtime/javascript.
The editor.html in the same location also works.

doc/tutorial/gf-tutorial.t2t

@@ -4968,7 +4968,7 @@ some other JavaScript and HTML files; these files can be used
 as templates for building applications.
 
 An example of usage is
-[``translator.html`` http://grammaticalframework.org:41296],
+[``translator.html`` ../../src/runtime/javascript/translator.html],
 which is in fact initialized with
 a pointer to the Food grammar, so that it provides translation between the English
 and Italian grammars: