website/docs: finalize release notes for 2025.6 (#14854)

* remove internal changes from release notes

* add late additions to release notes

* remove release candidate notice from `2025.6`

* rotate supported versions

* rotate releases in sidebar

* Revert "rotate supported versions"

This reverts commit eea9d03e1d.

I'd like to do the release tonight, but I can't merge this because it
needs a review from @teams/security. I'll open a separate PR for it.

website/sidebars/docs.mjs

@@ -10,13 +10,14 @@ import { generateVersionDropdown } from "../src/utils.js";
  * @type {SidebarItemConfig[]}
  */
 const releases = [
+    "releases/2025/v2025.6",
     "releases/2025/v2025.4",
     "releases/2025/v2025.2",
-    "releases/2024/v2024.12",
     {
         type: "category",
         label: "Previous versions",
         items: [
+            "releases/2024/v2024.12",
             "releases/2024/v2024.10",
             "releases/2024/v2024.8",
             "releases/2024/v2024.6",