docs: remove changelog link from sidebar (#12459)

The changelog page on zitadel.com was removed for being unmaintained,
leaving the docs sidebar link 404ing.

Co-authored-by: Rajat Singh <[email protected]>

apps/docs/lib/sidebar-data.ts

@@ -870,17 +870,6 @@ export const guidesSidebar: readonly SidebarItem[] = [
         id: "product/roadmap",
         label: "Roadmap",
       },
-      {
-        type: "category",
-        label: "Releases",
-        items: [
-          {
-            type: "link",
-            label: "Changelog",
-            href: "https://zitadel.com/changelog",
-          },
-        ],
-      },
       {
         type: "category",
         label: "Support Resources",