Update pytest requirement from 8.1.1 to 8.3.4 in /backend

Updates the requirements on [pytest](https://github.com/pytest-dev/pytest) to permit the latest version.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/main/CHANGELOG.rst)
- [Commits](pytest-dev/pytest@8.1.1...8.3.4)

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

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

backend/pyproject.toml

@@ -59,7 +59,7 @@ trio = "0.25.0"
 uvicorn = "0.30.6"
 openai = "1.43.0"
 pre-commit="3.7.0"
-pytest="8.1.1"
+pytest="8.3.4"
 datasets = "2.21.0"
 lancedb = "^0.12.0"