Update broken link to singleton types

Author: joan38

docs/_includes/features.html

@@ -9,7 +9,7 @@ <h1 id="so-features">So, features?</h1>
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-                        <td><a href="http://dotty.epfl.ch/docs/reference/union-types.html">Union</a>, <a href="http://dotty.epfl.ch/docs/reference/intersection-types.html">intersection</a> and <a href="http://docs.scala-lang.org/sips/pending/42.type.html">literal singleton types</a></td>
+                        <td><a href="http://dotty.epfl.ch/docs/reference/union-types.html">Union</a>, <a href="http://dotty.epfl.ch/docs/reference/intersection-types.html">intersection</a> and <a href="http://dotty.epfl.ch/docs/reference/singleton-types.html">literal singleton types</a></td>
                         <td>Implemented</td>
                     </tr>
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