[DOCS] Fix hard-coded links (elastic#209433)

(cherry picked from commit d7fe75a)

Author: lcawl

docs/osquery/osquery.asciidoc

@@ -394,7 +394,7 @@ This is useful for teams who need in-depth and detailed control.
 The https://github.com/osquery/osquery/releases[Osquery version] available on an Elastic Agent
 is associated to the version of Osquery Beat on the Agent.
 To get the latest version of Osquery Beat,
-https://www.elastic.co/guide/en/fleet/master/upgrade-elastic-agent.html[upgrade your Elastic Agent].
+{fleet-guide}/upgrade-elastic-agent.html[upgrade your Elastic Agent].
 
 [float]
 == Debug issues