ref(koa): Remove unused koa router import (#11771)

Author: AbhiPrasad

platform-includes/getting-started-use/javascript.koa.mdx

@@ -4,10 +4,8 @@ require("./instrument");
 
 // Now require other modules
 const Koa = require("koa");
-const Router = require("@koa/router");
 const Sentry = require("@sentry/node");
 
-const router = new Router();
 const app = new Koa();
 
 Sentry.setupKoaErrorHandler(app);
@@ -23,10 +21,8 @@ import "./instrument";
 
 // Now import other modules
 import Koa from "koa";
-import Router from "@koa/router";
 import * as Sentry from "@sentry/node";
 
-const router = new Router();
 const app = new Koa();
 
 Sentry.setupKoaErrorHandler(app);