fix broken markdown local links in 2020/endoh2/README.md

Ran `bin/readme2index.sh -v 1 2020/endoh2` to perform the above.

2020/endoh2/README.md

@@ -29,11 +29,11 @@ What happens if you do
 
 ## Judges' remarks:
 
-Clever use of the C99 complex data type. The [spoiler](spoiler.html) directory
+Clever use of the C99 complex data type. The [spoiler](spoiler/spoiler.html) directory
 contains clues as to how some winning authors create / edit programs into ASCII
 shapes.
 
-With the source from the [spoiler](spoiler.html) directory could you make the code
+With the source from the [spoiler](spoiler/spoiler.html) directory could you make the code
 render for a larger terminal window?  How about adding more glyphs?
 
 

2020/endoh2/index.html

@@ -407,10 +407,10 @@ Location: <a href="../../location.html#JP">JP</a> - <em>Japan</em></li>
 <pre><code>    ./prog prog.c</code></pre>
 <p>?</p>
 <h2 id="judges-remarks">Judges’ remarks:</h2>
-<p>Clever use of the C99 complex data type. The <a href="spoiler.html">spoiler</a> directory
+<p>Clever use of the C99 complex data type. The <a href="spoiler/spoiler.html">spoiler</a> directory
 contains clues as to how some winning authors create / edit programs into ASCII
 shapes.</p>
-<p>With the source from the <a href="spoiler.html">spoiler</a> directory could you make the code
+<p>With the source from the <a href="spoiler/spoiler.html">spoiler</a> directory could you make the code
 render for a larger terminal window? How about adding more glyphs?</p>
 <h2 id="authors-remarks">Author’s remarks:</h2>
 <p>No! Try not. Do, or do not. There is no try.</p>