Update banner.html

Author: AmandaPerino

_includes/banner.html

@@ -1,7 +1,7 @@
 <div class="banner text--align-center">
   <p>
     <a class="common-button--text" href="https://rubyonrails.org/world/2025" target="_blank">
-      [Rails World 2025] General Admission tickets available - Book now
+      [Rails World 2025 is sold out] See you in Amsterdam!
     </a>
   </p>
 </div>