Bump streamdown from 1.4.0 to 1.6.9 (#269)

Bumps [streamdown](https://github.com/vercel/streamdown/tree/HEAD/packages/streamdown) from 1.4.0 to 1.6.9.
- [Release notes](https://github.com/vercel/streamdown/releases)
- [Changelog](https://github.com/vercel/streamdown/blob/main/packages/streamdown/CHANGELOG.md)
- [Commits](https://github.com/vercel/streamdown/commits/[email protected]/packages/streamdown)

---
updated-dependencies:
- dependency-name: streamdown
  dependency-version: 1.6.9
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

packages/elements/package.json

@@ -23,7 +23,7 @@
     "react": "19.2.1",
     "react-dom": "19.2.1",
     "shiki": "3.15.0",
-    "streamdown": "^1.4.0",
+    "streamdown": "^1.6.10",
     "tokenlens": "^1.3.1",
     "use-stick-to-bottom": "^1.1.1"
   },