Update @types/koa-router requirement from 7.0.38 to 7.0.39 (#4052)

Updates the requirements on [@types/koa-router](https://github.com/DefinitelyTyped/DefinitelyTyped) to permit the latest version.
- [Release notes](https://github.com/DefinitelyTyped/DefinitelyTyped/releases)
- [Commits](https://github.com/DefinitelyTyped/DefinitelyTyped/commits

)

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