Improve unknown-key validation error message in @kbn/config-schema#258633

hammad-nasir-elastic merged 2 commits intoelastic:mainelastic/kibana:mainfrom

hammad-nasir-elastic:fix/improve-config-schema-unknown-key-error-messagehammad-nasir-elastic/kibana-nasir:fix/improve-config-schema-unknown-key-error-messageCopy head branch name to clipboard