chore(deps): bump koa and @types/koa

Bumps [koa](https://github.com/koajs/koa) and [@types/koa](https://github.com/DefinitelyTyped/DefinitelyTyped/tree/HEAD/types/koa). These dependencies needed to be updated together.

Updates `koa` from 3.0.3 to 3.1.1
- [Release notes](https://github.com/koajs/koa/releases)
- [Changelog](https://github.com/koajs/koa/blob/master/History.md)
- [Commits](koajs/koa@v3.0.3...v3.1.1)

Updates `@types/koa` from 3.0.0 to 3.0.1
- [Release notes](https://github.com/DefinitelyTyped/DefinitelyTyped/releases)
- [Commits](https://github.com/DefinitelyTyped/DefinitelyTyped/commits/HEAD/types/koa)

---
updated-dependencies:
- dependency-name: koa
  dependency-version: 3.1.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: "@types/koa"
  dependency-version: 3.0.1
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Author: dependabot[bot]