Bump requests from 2.15.1 to 2.20.0

Bumps [requests](https://github.com/psf/requests) from 2.15.1 to 2.20.0.
- [Release notes](https://github.com/psf/requests/releases)
- [Changelog](https://github.com/psf/requests/blob/main/HISTORY.md)
- [Commits](psf/requests@v2.15.1...v2.20.0)

---
updated-dependencies:
- dependency-name: requests
  dependency-type: indirect
...

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