fix emloty 2nd level header warning

Removed empty 2nd level header from top level `index.html`
to remove Nu HTML check warning.

Run `make gen_top_html` to perform the above and test under macOS.

inc/header.no-header-2.html

@@ -0,0 +1,8 @@
+<!-- START: this line starts content from: inc/header.default.html -->
+
+<div class="header">
+  <img src="%%DOCROOT_SLASH%%png/ioccc.png" alt="IOCCC image by Matt Zucker" width=300 height=110>
+  <h1>%%HEADER_1%%</h1>
+</div>
+
+<!-- END: this line ends content from: inc/header.default.html -->

inc/md2html.cfg

@@ -174,8 +174,8 @@ index.md
 	DESCRIPTION=International Obfuscated C Code Contest
 	-s
 	KEYWORDS=IOCCC, International, Obfuscated, C, c, IOCCC, ioccc, obfuscated, Obfuscate, obfuscate, Landon Curt Noll, chongo, Leonid A. Broukhis, leob
-	-s
-	HEADER_2=
+	-H
+	header=no-header-2
 	-D
 	./
 

index.html

@@ -46,7 +46,6 @@
 <div class="header">
   <img src="./png/ioccc.png" alt="IOCCC image by Matt Zucker" width=300 height=110>
   <h1>The International Obfuscated C Code Contest</h1>
-  <h2></h2>
 </div>
 
 <!-- END: this line ends content from: inc/header.default.html -->