improved the h2 title for HTML from markdown other than README.md

For HTML files from markdown files other than README.md, the h2
title now refers to the HTML file instead of the markdown file.

Changed `bin/gen-other-html.sh` VERSION from "1.2.3 2024-04-28"
to "1.2.4 2024-05-31" to perform the above.

Perform `make www` to perform the above and test under macOS.

2018/ferguson/FILES.html

@@ -363,7 +363,7 @@
 	   height=110>
   </a>
   <h1>The International Obfuscated C Code Contest</h1>
-  <h2>FILES.md for 2018/ferguson</h2>
+  <h2>FILES.html for 2018/ferguson</h2>
 </div>
 
 <!-- END: this line ends content from: inc/header.default.html -->

2018/ferguson/rpm.html

@@ -363,7 +363,7 @@
 	   height=110>
   </a>
   <h1>The International Obfuscated C Code Contest</h1>
-  <h2>rpm.md for 2018/ferguson</h2>
+  <h2>rpm.html for 2018/ferguson</h2>
 </div>
 
 <!-- END: this line ends content from: inc/header.default.html -->