Bump koa from 2.16.3 to 3.1.2

Bumps [koa](https://github.com/koajs/koa) from 2.16.3 to 3.1.2.
- [Release notes](https://github.com/koajs/koa/releases)
- [Changelog](https://github.com/koajs/koa/blob/master/History.md)
- [Commits](koajs/koa@v2.16.3...v3.1.2)

---
updated-dependencies:
- dependency-name: koa
  dependency-version: 3.1.2
  dependency-type: direct:production
...

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

Author: dependabot[bot]

package-lock.json

@@ -47,7 +47,7 @@
     "@uswitch/koa-timeout": "^1.7.1",
     "@uswitch/koa-tracer": "^1.8.1",
     "@uswitch/koa-zipkin": "^1.12.1",
-    "koa": "^2.15.4",
+    "koa": "^3.1.2",
     "koa-bodyparser": "^4.2.1",
     "koa-compose": "^4.1.0",
     "koa-helmet": "^4.0.0",