chore(deps): bump langchain-community from 0.2.0 to 0.2.6 in /backend

Bumps [langchain-community](https://github.com/langchain-ai/langchain) from 0.2.0 to 0.2.6.
- [Release notes](https://github.com/langchain-ai/langchain/releases)
- [Commits](https://github.com/langchain-ai/langchain/compare/langchain-community==0.2.0...langchain-community==0.2.6

)

---
updated-dependencies:
- dependency-name: langchain-community
  dependency-type: direct:production
  update-type: version-update:semver-patch
...
Signed-off-by: dependabot[bot] <support@github.com>

backend/requirements.txt

@@ -31,7 +31,7 @@ anthropic
 google-generativeai==0.5.4
 
 langchain==0.2.0
-langchain-community==0.2.0
+langchain-community==0.2.6
 langchain-chroma==0.1.2
 
 fake-useragent==1.5.1