Bump pandas from 2.1.2 to 2.1.3 in /testdata (#25)

Bumps [pandas](https://github.com/pandas-dev/pandas) from 2.1.2 to 2.1.3.
- [Release notes](https://github.com/pandas-dev/pandas/releases)
- [Commits](pandas-dev/pandas@v2.1.2...v2.1.3)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

testdata/requirements.txt

@@ -2,4 +2,4 @@ xgboost==1.6.0
 scikit-learn==1.3.2
 treelite==3.9.1
 treelite-runtime==3.9.1
-pandas==2.1.2
+pandas==2.1.3