Bump koa from 2.6.2 to 2.7.0

Bumps [koa](https://github.com/koajs/koa) from 2.6.2 to 2.7.0.
- [Release notes](https://github.com/koajs/koa/releases)
- [Changelog](https://github.com/koajs/koa/blob/master/History.md)
- [Commits](koajs/koa@2.6.2...2.7.0)

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

package.json

@@ -31,7 +31,7 @@
     "browserify": "^16.2.3",
     "dog-names": "^1.0.2",
     "ioredis": "^4.6.2",
-    "koa": "^2.6.2",
+    "koa": "^2.7.0",
     "koa-router": "^7.4.0",
     "koa-static": "^5.0.0",
     "mz": "^2.7.0",