[Suggestion] Document that Elastic Defend response actions don't work if an alternate cluster is being used for output

[ferullo]

What can we change to make the docs better?

Endpoint response actions don't work when a second/alternate cluster is used as the output target in Fleet. The issue is that response action state management information is in the primary cluster (the one with Fleet) but Endpoint writes actual result data to the alternate cluster. Until this is fixed, we should document it as a limitation.

cc @raqueltabuyo @caitlinbetz @dasansol92

Doc URL

Please include the doc URL and any other related information where applicable:
Doc URL:
Github issue link(s)/Other resources:

Which documentation set needs improvement?

ESS and serverless

Software version

This has been the case since cross cluster support has existed in Fleet and Response Actions have existed for Defend.