Bump pandas from 1.2.0 to 1.2.1 (#467)

Bumps [pandas](https://github.com/pandas-dev/pandas) from 1.2.0 to 1.2.1.
- [Release notes](https://github.com/pandas-dev/pandas/releases)
- [Changelog](https://github.com/pandas-dev/pandas/blob/master/RELEASE.md)
- [Commits](https://github.com/pandas-dev/pandas/compare/v1.2.0...v1.2.1)

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

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

requirements.txt

@@ -1,6 +1,6 @@
 numpy == 1.19.5
 scipy == 1.6.0
-pandas == 1.2.0
+pandas == 1.2.1
 matplotlib == 3.3.3
 cvxpy == 1.1.7
 pytest == 6.2.2