Bump pandas from 1.3.0 to 1.3.1 (AtsushiSakai#532)

Bumps [pandas](https://github.com/pandas-dev/pandas) from 1.3.0 to 1.3.1.
- [Release notes](https://github.com/pandas-dev/pandas/releases)
- [Changelog](https://github.com/pandas-dev/pandas/blob/master/RELEASE.md)
- [Commits](pandas-dev/pandas@v1.3.0...v1.3.1)

---
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>

Author: dependabot[bot]

requirements.txt

@@ -1,5 +1,5 @@
 numpy == 1.21.1
 scipy == 1.7.0
-pandas == 1.3.0
+pandas == 1.3.1
 matplotlib == 3.4.2
 cvxpy == 1.1.13