Bump langchain from 0.0.340 to 0.2.7

Bumps [langchain](https://github.com/langchain-ai/langchain) from 0.0.340 to 0.2.7.
- [Release notes](https://github.com/langchain-ai/langchain/releases)
- [Commits](langchain-ai/langchain@v0.0.340...langchain==0.2.7)

---
updated-dependencies:
- dependency-name: langchain
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

requirements-dev.txt

@@ -4,7 +4,7 @@ Markdown==3.4.4
 requests==2.31.0
 tqdm==4.66.1
 tiktoken==0.4.0
-langchain==0.0.340
+langchain==0.2.7
 bs4==0.0.1
 urllib3==2.1.0
 pytest==7.4.0