Doc Feedback: Clustering Gateways and Key Managers with key caching

[Christopher-Davey]

Location : https://apim.docs.wso2.com/en/latest/deploy-and-publish/deploy-on-gateway/api-gateway/scaling-the-gateway/ This needs updating with reference to the new gateway / control plane deployment patterns for 4.x which does not mention deploying the key manager separately.

[nandika]

Added as a task to completed