Bump @types/koa from 2.11.6 to 2.13.1

Bumps [@types/koa](https://github.com/DefinitelyTyped/DefinitelyTyped/tree/HEAD/types/koa) from 2.11.6 to 2.13.1.
- [Release notes](https://github.com/DefinitelyTyped/DefinitelyTyped/releases)
- [Commits](https://github.com/DefinitelyTyped/DefinitelyTyped/commits/HEAD/types/koa)

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

Author: dependabot-preview[bot]

package-lock.json

@@ -37,7 +37,7 @@
     "@types/chai": "^4.2.14",
     "@types/chai-as-promised": "^7.1.3",
     "@types/express": "^4.17.11",
-    "@types/koa": "^2.11.6",
+    "@types/koa": "^2.13.1",
     "@types/mocha": "^8.2.0",
     "@types/node": "^14.14.31",
     "@types/sinon": "^9.0.10",