Agent upgrade order (#2521) (#2522)

* Add link in air-gapped docs to Elastic Agent requirements

* Remove trailing space causing extra diff

(cherry picked from commit b59aa76)

Co-authored-by: David Kilfoyle <[email protected]>

Author: mergify[bot]

docs/en/install-upgrade/air-gapped-install.asciidoc

@@ -94,7 +94,7 @@ Air-gapped install of {agent} depends on the <<air-gapped-elastic-package-regist
 
 Additionally, if the {agent} {elastic-defend} integration is used, then access to the <<air-gapped-elastic-endpoint-artifact-repository,Elastic Endpoint Artifact Repository>> is necessary in order to deploy updates for some of the detection and prevention capabilities.
 
-To learn more about install and configuration, refer to the {fleet-guide}/elastic-agent-installation.html[{agent} install documentation].
+To learn more about install and configuration, refer to the {fleet-guide}/elastic-agent-installation.html[{agent} install documentation]. Make sure to check the requirements specific to running {agents} in an {fleet-guide}/air-gapped.html[air-gapped environment]. 
 
 To get a better understanding of how to work with {agent} configuration settings and policies, refer to <<air-gapped-agent-integration-guide>>.