Change Prebuilt Security Rules Changelog Reference (#156716)

## Summary
This PR changes the URL reference link from Kibana UI to downloadable
updates security docs site. The current link directs the user to the
security doc updates that relate to file system rule updates, which is
now deprecated. This update would point the user to the downloadable OOB
package updates which is how we currently release prebuilt rules.

Existing:
https://www.elastic.co/guide/en/security/master/prebuilt-rules-changelog.html
(docs built from filesystem rules - deprecated)
Proposed:
https://www.elastic.co/guide/en/security/master/prebuilt-rules-downloadable-updates.html
(aligns with OOB packages - currently how we release and build docs)

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

@@ -382,7 +382,7 @@ export const getDocLinks = ({ kibanaBranch }: GetDocLinkOptions): DocLinks => {
       gettingStarted: `${SECURITY_SOLUTION_DOCS}index.html`,
       privileges: `${SECURITY_SOLUTION_DOCS}sec-requirements.html`,
       ml: `${SECURITY_SOLUTION_DOCS}machine-learning.html`,
-      ruleChangeLog: `${SECURITY_SOLUTION_DOCS}prebuilt-rules-changelog.html`,
+      ruleChangeLog: `${SECURITY_SOLUTION_DOCS}prebuilt-rules-downloadable-updates.html`,
       detectionsReq: `${SECURITY_SOLUTION_DOCS}detections-permissions-section.html`,
       networkMap: `${SECURITY_SOLUTION_DOCS}conf-map-ui.html`,
       troubleshootGaps: `${SECURITY_SOLUTION_DOCS}alerts-ui-monitor.html#troubleshoot-gaps`,