chore(deps): bump openai in /.github/actions/generate-blog-post

Bumps [openai](https://github.com/openai/openai-node) from 6.18.0 to 6.21.0.
- [Release notes](https://github.com/openai/openai-node/releases)
- [Changelog](https://github.com/openai/openai-node/blob/master/CHANGELOG.md)
- [Commits](openai/openai-node@v6.18.0...v6.21.0)

---
updated-dependencies:
- dependency-name: openai
  dependency-version: 6.21.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

.github/actions/generate-blog-post/package-lock.json

@@ -17,6 +17,6 @@
   "license": "0BSD",
   "dependencies": {
     "humanize-ai-lib": "^1.0.0",
-    "openai": "^6.18.0"
+    "openai": "^6.21.0"
   }
 }