Bump pandas from 2.1.1 to 2.1.3 in /etc/requirements_dependabot

Bumps [pandas](https://github.com/pandas-dev/pandas) from 2.1.1 to 2.1.3.
- [Release notes](https://github.com/pandas-dev/pandas/releases)
- [Commits](pandas-dev/pandas@v2.1.1...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]>

etc/requirements_dependabot/requirements_tests.txt

@@ -105,7 +105,7 @@ packaging==23.2
     #   black
     #   matplotlib
     #   pytest
-pandas==2.1.1
+pandas==2.1.3
     # via
     #   bqplot
     #   exchange-calendars