chore(deps-dev): bump langchain from 0.2.18 to 0.2.20

Bumps [langchain](https://github.com/langchain-ai/langchainjs) from 0.2.18 to 0.2.20.
- [Release notes](https://github.com/langchain-ai/langchainjs/releases)
- [Changelog](https://github.com/langchain-ai/langchainjs/blob/main/release_workspace.js)
- [Commits](https://github.com/langchain-ai/langchainjs/commits)

---
updated-dependencies:
- dependency-name: langchain
  dependency-type: direct:development
...

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

package.json

@@ -105,7 +105,7 @@
     "esbuild-plugin-umd-wrapper": "3.0.0",
     "eslint": "8.57.0",
     "eslint-plugin-react-hooks": "4.6.2",
-    "langchain": "0.2.18",
+    "langchain": "0.2.20",
     "mocha": "10.7.3",
     "npm-run-all": "4.1.5",
     "react": "17.0.2",