Fix markup confusion in errata

Author: marijnh

html/errata.html

@@ -35,7 +35,7 @@ <h2>Chapter 10</h2>
 
 <h2>Chapter 20</h2>
 
-<p><strong>Page 369</strong> (Directory Creation): `MKCOL` stands for
+<p><strong>Page 369</strong> (Directory Creation): <code>MKCOL</code> stands for
 "make collection", not "make column" as the book claims.</p>
 
 </article>