Update index.html for 0.25

Author: mulle-nat

index.html

@@ -134,7 +134,7 @@ <h2>+[mulle-objc install]</h2>
       See <a href="//github.com/MulleFoundation/foundation-developer#install">foundation-developer</a>
       for installation instructions.
       <p>
-      Read the latest <a href="https://www.mulle-kybernetik.com/weblog/2024/mulle_objc_0_23_release.html">release announcement for version 0.23.1</a> for what's new.
+      Read the latest <a href="https://www.mulle-kybernetik.com/weblog/2024/mulle_objc_0_25_release.html">release announcement for version 0.25</a> for what's new.
       </section>
 
       <section class="keep-together">