chore(deps): Bump @netlify/functions in /functions/newsletter

Bumps [@netlify/functions](https://github.com/netlify/functions) from 1.6.0 to 2.4.0.
- [Release notes](https://github.com/netlify/functions/releases)
- [Changelog](https://github.com/netlify/functions/blob/main/CHANGELOG.md)
- [Commits](netlify/functions@v1.6.0...v2.4.0)

---
updated-dependencies:
- dependency-name: "@netlify/functions"
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

functions/newsletter/package.json

@@ -14,7 +14,7 @@
   "author": "Netlify",
   "license": "MIT",
   "dependencies": {
-    "@netlify/functions": "^1.6.0",
+    "@netlify/functions": "^2.4.0",
     "@types/node": "^20.7.0",
     "node-fetch": "^3.3.0",
     "typescript": "^5.1.3"