build(deps): bump pandas from 2.0.3 to 2.1.0 in /backend

Bumps [pandas](https://github.com/pandas-dev/pandas) from 2.0.3 to 2.1.0.
- [Release notes](https://github.com/pandas-dev/pandas/releases)
- [Commits](pandas-dev/pandas@v2.0.3...v2.1.0)

---
updated-dependencies:
- dependency-name: pandas
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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