fix(docs): broken link to preview

Signed-off-by: Gabriele Bartolini <[email protected]> f297761

Author: gbartolini

docs/index.html

@@ -139,7 +139,7 @@ <h1 class="text-xl">Documentation</h1>
 <p class="text-sm">Documentation by version</p>
 
 <p class="ml-6">
-    <a href="/documentation/1.28">v1.28.0-rc1</a> - released on <a
+    <a href="/documentation/preview">v1.28.0-rc1</a> - released on <a
         href="https://github.com/cloudnative-pg/cloudnative-pg/releases/tag/v1.28.0-rc1">07 Nov 2025</a>
 </p>