Fix a typo

Maybe it would be better to name that link `Index` or just `Table of Contents`?

Author: elkuku

frontend/encore/simple-example.rst

@@ -202,4 +202,4 @@ If those entries include CSS/Sass files (e.g. ``homepage.js`` requires
 Keep Going!
 -----------
 
-Go back to the :ref:`Encore Top List <encore-toc>` to learn more and add new features.
+Go back to the :ref:`Encore Toc List <encore-toc>` to learn more and add new features.