Build(deps): bump langchain from 0.2.6 to 0.2.8 (#59)

Bumps [langchain](https://github.com/langchain-ai/langchainjs) from 0.2.6 to 0.2.8.
- [Release notes](https://github.com/langchain-ai/langchainjs/releases)
- [Changelog](https://github.com/langchain-ai/langchainjs/blob/main/release_workspace.js)
- [Commits](langchain-ai/langchainjs@0.2.6...0.2.8)

---
updated-dependencies:
- dependency-name: langchain
  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

@@ -40,7 +40,7 @@
     "@langchain/core": "^0.2.9",
     "@langchain/openai": "^0.2.1",
     "cheerio": "^1.0.0-rc.12",
-    "langchain": "^0.2.6",
+    "langchain": "^0.2.8",
     "neo4j-driver": "^5.22.0",
     "zod": "^3.23.8"
   }