[Elastic Agent] Add a known issue for agents getting stuck in a scheduled state #2285
Description
Add a known issue in the release notes for the bug described in elastic/elastic-agent#8778 where after scheduling an agent upgrade and cancelling the upgrade action, the agents are stuck in scheduled state.
Affected releases: 8.18.x and 9.x
Workaround: Use the Fleet upgrade API with the force parameter set to true to force upgrade the agent