convert more spoiler into deobfuscation

2020/ferguson1/gameplay.html

@@ -802,7 +802,7 @@ to be a problem simply do:</p>
 could also set the max size to be the highest possible by saying</p>
 <pre><code>    MAXSIZE=-1</code></pre>
 <p>Which I’ve done in the <a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2020/ferguson1/play.sh">play.sh</a> script.</p>
-<p>I discuss how this mode works in [spoilers.markdown][].</p>
+<p>I discuss how this mode works in <a href="spoilers.html">spoilers.html</a>.</p>
 <p>Here’s an example run where I spelt ‘SNAKE’. As you can see it’s far from
 perfect: the snake after all does not leave gaps and the game does not support
 diagonal movement and I also made a mistake and had to modify what I was aiming