chore(deps-dev): bump @types/koa from 2.14.0 to 2.15.0 (#6601)

Bumps [@types/koa](https://github.com/DefinitelyTyped/DefinitelyTyped/tree/HEAD/types/koa) from 2.14.0 to 2.15.0.
- [Release notes](https://github.com/DefinitelyTyped/DefinitelyTyped/releases)
- [Commits](https://github.com/DefinitelyTyped/DefinitelyTyped/commits/HEAD/types/koa)

---
updated-dependencies:
- dependency-name: "@types/koa"
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

package.json

@@ -258,7 +258,7 @@
     "@types/jest": "^29.5.12",
     "@types/jsonwebtoken": "^8.5.9",
     "@types/katex": "^0.16.0",
-    "@types/koa": "^2.14.0",
+    "@types/koa": "^2.15.0",
     "@types/koa-compress": "^4.0.6",
     "@types/koa-helmet": "^6.0.8",
     "@types/koa-logger": "^3.1.5",