Update koa requirement from 2.6.1 to 2.6.2 (#3386)

Updates the requirements on [koa](https://github.com/koajs/koa) to permit the latest version.
- [Release notes](https://github.com/koajs/koa/releases)
- [Changelog](https://github.com/koajs/koa/blob/master/History.md)
- [Commits](https://github.com/koajs/koa/commits/2.6.2)

Signed-off-by: dependabot[bot] <support@dependabot.com>

package.json

@@ -143,7 +143,7 @@
 		"json5": "2.1.0",
 		"json5-loader": "1.0.1",
 		"katex": "0.10.0",
-		"koa": "2.6.1",
+		"koa": "2.6.2",
 		"koa-bodyparser": "4.2.1",
 		"koa-compress": "3.0.0",
 		"koa-favicon": "2.0.1",