Bump tavily-python from 0.2.6 to 0.2.8

Bumps [tavily-python](https://github.com/assafelovic/tavily-python) from 0.2.6 to 0.2.8.
- [Commits](https://github.com/assafelovic/tavily-python/commits)

---
updated-dependencies:
- dependency-name: tavily-python
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

requirements.txt

@@ -16,7 +16,7 @@ fastapi==0.104.1
 python-multipart==0.0.6
 markdown==3.5.1
 langchain==0.0.335
-tavily-python==0.2.6
+tavily-python==0.2.8
 permchain==0.0.3
 arxiv==2.0.0
 PyMuPDF==1.23.6