Doc: Fix upgrade TOC structure (#17361) (#17382)

(cherry picked from commit 960d997e9f)

Co-authored-by: Karen Metts <35154725+karenzone@users.noreply.github.com>

docs/reference/docker.md

@@ -22,7 +22,7 @@ However, version 9.0.0 of Logstash has not yet been released, so no Docker image
 
 Although it’s optional, we highly recommend verifying the signatures included with your downloaded Docker images to ensure that the images are valid.
 
-Elastic images are signed with [Cosign](https://docs.sigstore.dev/cosign/overview/) which is part of the [Sigstore](https://www.sigstore.dev/) project. Cosign supports container signing, verification, and storage in an OCI registry. Install the appropriate [Cosign application](https://docs.sigstore.dev/cosign/installation/) for your operating system.
+Elastic images are signed with [Cosign](https://docs.sigstore.dev/quickstart/quickstart-cosign/) which is part of the [Sigstore](https://www.sigstore.dev/) project. Cosign supports container signing, verification, and storage in an OCI registry. Install the appropriate Cosign application for your operating system.
 
 Run the following commands to verify the container image signature for {{ls}} v9.0.0-beta1:
 

docs/reference/toc.yml

@@ -27,10 +27,11 @@ toc:
       - file: logging.md
       - file: shutdown.md
   - file: upgrading-logstash.md
-  - file: upgrading-using-package-managers.md
-  - file: upgrading-using-direct-download.md
-  - file: upgrading-minor-versions.md
-  - file: upgrading-logstash-9-0.md
+    children:
+      - file: upgrading-using-package-managers.md
+      - file: upgrading-using-direct-download.md
+      - file: upgrading-minor-versions.md
+      - file: upgrading-logstash-9-0.md
   - file: creating-logstash-pipeline.md
     children:
       - file: configuration-file-structure.md

docs/reference/upgrading-logstash.md

@@ -21,12 +21,12 @@ While upgrading Logstash:
 
 If you’re upgrading other products in the stack, also read the [Elastic Stack Installation and Upgrade Guide](docs-content://deploy-manage/index.md).
 
-See the following topics for information about upgrading Logstash:
+See these topics for information about upgrading Logstash:
 
 * [Upgrading using package managers](/reference/upgrading-using-package-managers.md)
 * [Upgrading using a direct download](/reference/upgrading-using-direct-download.md)
 * [Upgrading between minor versions](/reference/upgrading-minor-versions.md)
-* [Upgrading Logstash to 9.0](https://www.elastic.co/guide/en/logstash/master/upgrading-logstash-9.0.html)
+* [Upgrading Logstash to 9.0](/reference/upgrading-logstash-9-0.md)
 
 
 ## When to upgrade [_when_to_upgrade]

docs/release-notes/breaking-changes.md

@@ -18,7 +18,7 @@ To learn how to upgrade, check out <uprade docs>.
 % ::::
 
 ## 9.0.0 [logstash-900-breaking-changes]
-**Release date:** March 25, 2025
+**Release date:** April 2, 2025
 
 ### Changes to SSL settings in {{ls}} plugins [ssl-settings-9.0]
 We’ve removed deprecated SSL settings in some {{ls}} plugins, and have replaced them with updated settings. If your plugin configuration contains any of these obsolete options, the plugin may fail to start.

docs/release-notes/index.md

@@ -23,7 +23,7 @@ To check for security updates, go to [Security announcements for the Elastic sta
 % *
 
 ## 9.0.0 [logstash-900-release-notes]
-**Release date:** March 25, 2025
+**Release date:** April 2, 2025
 
 ### Features and enhancements [logstash-900-features-enhancements]