Bump pandas from 0.25.1 to 0.25.2

Bumps [pandas](https://github.com/pandas-dev/pandas) from 0.25.1 to 0.25.2.
- [Release notes](https://github.com/pandas-dev/pandas/releases)
- [Changelog](https://github.com/pandas-dev/pandas/blob/master/RELEASE.md)
- [Commits](pandas-dev/pandas@v0.25.1...v0.25.2)

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

requirements.txt

@@ -1,4 +1,4 @@
-pandas==0.25.1
+pandas==0.25.2
 pymatgen==2019.10.16
 tensorflow==2.0.0
 keras==2.3.1