fix Support the IOCCC title on years.html

Fixed heading title for "Support the IOCCC" block in `years.html`.

Changed `bin/gen-years.sh` VERSION from  "2.1.0 2025-06-06"
to "2.1.1 2025-06-06".

Update sitemap.

Tested the above via `make gen_years timestamp` on macOS.

sitemap.xml

@@ -15278,7 +15278,7 @@
 </url>
 <url>
     <loc>https://www.ioccc.org/bin/gen-years.sh</loc>
-    <lastmod>2025-06-07T02:00:47+00:00</lastmod>
+    <lastmod>2025-06-07T02:36:45+00:00</lastmod>
 </url>
 <url>
     <loc>https://www.ioccc.org/bin/html.sed</loc>
@@ -15626,6 +15626,6 @@
 </url>
 <url>
     <loc>https://www.ioccc.org/years.html</loc>
-    <lastmod>2025-06-07T02:03:18+00:00</lastmod>
+    <lastmod>2025-06-07T02:38:29+00:00</lastmod>
 </url>
 </urlset>