fix links in entry HTML files other than index.html

Fixed internal links in entry HTML files other than index.html.

Removed links to markdown files that otherwise used to
generate HTML files other than index.html.

Ran `make gen_other_html` to perform the above.

2020/ferguson1/cannibalism.log.html

@@ -134,7 +134,8 @@
 <!-- START: this line starts content for HTML phase 21 by: bin/pandoc-wrapper.sh via bin/md2html.sh -->
 
 <!-- BEFORE: 1st line of markdown file: 2020/ferguson1/cannibalism.log.md -->
-<h1 id="extreme-cannibalism-in-2020-ioccc-dont-tread-on-me-snake-game">Extreme cannibalism in <a href="/2020/ferguson1/prog.c">2020 IOCCC ‘Don’t tread on me’ Snake game</a></h1>
+<h1 id="extreme-cannibalism-in-a-snake-game">Extreme cannibalism in a Snake game</h1>
+<p>See the <a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2020/ferguson1/prog.c">2020 IOCCC ‘Don’t tread on me’ Snake game source code</a>.</p>
 <p>To give an idea what cannibalism can look like (it’s I believe a unique feature
 to any other version of Snake), this file shows just how extreme cannibalism can
 get with a long snake. I made a few changes, described below, to make it easier