Format fix html files from 2019

2019/diels-grabsch1/index.html

@@ -432,7 +432,7 @@ compresses differently? The judges know. :)</p>
 <h4 id="check-for-correctness">Check for correctness:</h4>
 <pre><code>    zcat guidelines.txt.Z &gt; guidelines2.txt
     diff -s guidelines.txt guidelines2.txt</code></pre>
-<p>Of course you can also use <a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/mills2/prog.c">2015/mills2prog.c</a> instead of
+<p>Of course you can also use <a href="../../2015/mills2/index.html">2015/mills2</a> instead of
 <code>zcat</code> to verify the output file. The achieved compression ratio roughly matches
 that of the classic Unix <code>compress(1)</code> tool. And the source code is very
 compressed, too: It has exactly the same size as the paragraph you are reading