Bump koa from 2.15.0 to 2.15.1

Bumps [koa](https://github.com/koajs/koa) from 2.15.0 to 2.15.1.
- [Changelog](https://github.com/koajs/koa/blob/2.15.1/History.md)
- [Commits](koajs/koa@2.15.0...2.15.1)

---
updated-dependencies:
- dependency-name: koa
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]