chore(deps): bump koa from 2.15.0 to 2.15.3 (#7134)

Bumps [koa](https://github.com/koajs/koa) from 2.15.0 to 2.15.3.
- [Changelog](https://github.com/koajs/koa/blob/2.15.3/History.md)
- [Commits](https://github.com/koajs/koa/compare/2.15.0...2.15.3)

---
updated-dependencies:
- dependency-name: koa
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

package.json

@@ -133,7 +133,7 @@
     "jszip": "^3.10.1",
     "katex": "^0.16.10",
     "kbar": "0.1.0-beta.41",
-    "koa": "^2.15.0",
+    "koa": "^2.15.3",
     "koa-body": "^6.0.1",
     "koa-compress": "^5.1.1",
     "koa-helmet": "^6.1.0",