chore(deps): bump koa from 2.8.2 to 2.9.0

Bumps [koa](https://github.com/koajs/koa) from 2.8.2 to 2.9.0.
- [Release notes](https://github.com/koajs/koa/releases)
- [Changelog](https://github.com/koajs/koa/blob/master/History.md)
- [Commits](https://github.com/koajs/koa/compare/2.8.2...2.9.0)

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

package.json

@@ -77,7 +77,7 @@
     "iconv-lite": "0.5.0",
     "imgur": "0.3.1",
     "json-bigint": "0.3.0",
-    "koa": "2.8.2",
+    "koa": "2.9.0",
     "koa-basic-auth": "4.0.0",
     "koa-favicon": "2.0.1",
     "koa-mount": "4.0.0",

yarn.lock

@@ -6594,10 +6594,10 @@ koa-router@7.4.0:
     path-to-regexp "^1.1.1"
     urijs "^1.19.0"
 
-koa@2.8.2:
-  version "2.8.2"
-  resolved "https://registry.yarnpkg.com/koa/-/koa-2.8.2.tgz#dfba771a69c1a98e014826804e95132c00af6615"
-  integrity sha512-q1uZOgpl3wjr5FS/tjbABJ8lA5+NeKa9eq7QyBP5xxgOBwJN4iBrMEgO3LroE51lrIw3BsO0WZZ0Yi6giSiMDw==
+koa@2.9.0:
+  version "2.9.0"
+  resolved "https://registry.yarnpkg.com/koa/-/koa-2.9.0.tgz#ec957fc83cb2722fa56d26c1b2231d402d8542a2"
+  integrity sha512-Y1kb5wqcEm3FuFmPenIX3o61zbKVx+wy0p8kiG+DAv70WiTrnoupDQy8fpLYT6esaJmLdzgzmGbLCKcamw+VvA==
   dependencies:
     accepts "^1.3.5"
     cache-content-type "^1.0.0"