Fix the Upgrade Assistant Docs link to the Release doc page (elastic#…

…193269)

fixed: elastic#191849 

## Summary

This PR fix the `Check the latest release highlights` links in the
Upgrade Assistant to the correct latest release links.
The fix is ​​below
``` diff
// kibana/packages/kbn-doc-links/src/get_doc_links.ts
-      latestReleaseHighlights: `${ELASTIC_WEBSITE_URL}guide/en/elastic-stack/current/elastic-stack-highlights.html`,
+      latestReleaseHighlights: `${ELASTIC_WEBSITE_URL}guide/en/starting-with-the-elasticsearch-platform-and-its-solutions/current/new.html`,
```

PS: 
This is my first time to contribute to kibana. If there is anything that
needs to be modified, please give me some advice and I will try my best!


### For maintainers

- [x] This was checked for breaking API changes and was [labeled
appropriately](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)

Co-authored-by: florent-leborgne <[email protected]>

packages/kbn-doc-links/src/get_doc_links.ts

@@ -436,7 +436,7 @@ export const getDocLinks = ({ kibanaBranch, buildFlavor }: GetDocLinkOptions): D
       migrationApiDeprecation: `${ELASTICSEARCH_DOCS}migration-api-deprecation.html`,
       nodeRoles: `${ELASTICSEARCH_DOCS}modules-node.html#node-roles`,
       releaseHighlights: `${ELASTICSEARCH_DOCS}release-highlights.html`,
-      latestReleaseHighlights: `${ELASTIC_WEBSITE_URL}guide/en/elastic-stack/current/elastic-stack-highlights.html`,
+      latestReleaseHighlights: `${ELASTIC_WEBSITE_URL}guide/en/starting-with-the-elasticsearch-platform-and-its-solutions/current/new.html`,
       remoteClusters: `${ELASTICSEARCH_DOCS}remote-clusters.html`,
       remoteClustersProxy: `${ELASTICSEARCH_DOCS}remote-clusters.html#proxy-mode`,
       remoteClusersProxySettings: `${ELASTICSEARCH_DOCS}remote-clusters-settings.html#remote-cluster-proxy-settings`,