[koa-webpack] Fix build by adapting test to changes in webpack-dev-middleware (#22576)
[koa-webpack] Fix build by adapting test to changes in webpack-dev-middleware (#22576)


laurentiustamate94/DefinitelyTyped,AgentME/DefinitelyTyped,alexdresko/DefinitelyTyped,zuzusik/DefinitelyTyped,rolandzwaga/DefinitelyTyped,chrootsu/DefinitelyTyped,georgemarshall/DefinitelyTyped,AgentME/DefinitelyTyped,dsebastien/DefinitelyTyped,alexdresko/DefinitelyTyped,dsebastien/DefinitelyTyped,arusakov/DefinitelyTyped,mcliment/DefinitelyTyped,chrootsu/DefinitelyTyped,arusakov/DefinitelyTyped,zuzusik/DefinitelyTyped,arusakov/DefinitelyTyped,zuzusik/DefinitelyTyped,AgentME/DefinitelyTyped,markogresak/DefinitelyTyped,rolandzwaga/DefinitelyTyped,AgentME/DefinitelyTyped,borisyankov/DefinitelyTyped,georgemarshall/DefinitelyTyped,magny/DefinitelyTyped,borisyankov/DefinitelyTyped,one-pieces/DefinitelyTyped,georgemarshall/DefinitelyTyped,magny/DefinitelyTyped,georgemarshall/DefinitelyTyped