Fix banner link

Author: justinfagnani

packages/lit-dev-content/site/home/1-splash.html

@@ -1,7 +1,7 @@
 <section id="new-banner">
   <p>
     📣 Lit is now part of the OpenJS Foundation!
-    Read <a href="/blog/2025-10-14/">our announcement</a>.
+    Read <a href="/blog/2025-10-14-openjs/">our announcement</a>.
   </p>
 </section>
 <section id="intro">