Bump requests in /4_alpha_research_and_factor_modeling

Bumps [requests](https://github.com/psf/requests) from 2.18.4 to 2.20.0.
- [Release notes](https://github.com/psf/requests/releases)
- [Changelog](https://github.com/psf/requests/blob/master/HISTORY.md)
- [Commits](psf/requests@v2.18.4...v2.20.0)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

4_alpha_research_and_factor_modeling/requirements.txt

@@ -8,7 +8,7 @@ plotly==2.2.3
 pyparsing==2.2.0
 python-dateutil==2.6.1
 pytz==2017.3
-requests==2.18.4
+requests==2.20.0
 scipy==1.0.0
 scikit-learn==0.19.1
 six==1.11.0