Bump koa from 2.11.0 to 2.12.0

Bumps [koa](https://github.com/koajs/koa) from 2.11.0 to 2.12.0.
- [Release notes](https://github.com/koajs/koa/releases)
- [Changelog](https://github.com/koajs/koa/blob/master/History.md)
- [Commits](koajs/koa@2.11.0...2.12.0)

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

package.json

@@ -32,7 +32,7 @@
     "debug": "^4.1.1",
     "dog-names": "^2.0.0",
     "ioredis": "^4.17.1",
-    "koa": "^2.11.0",
+    "koa": "^2.12.0",
     "koa-router": "^8.0.8",
     "koa-static": "^5.0.0",
     "mz": "^2.7.0",