Bump requests from 2.18.4 to 2.20.0 in /intro-nfvis

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] <support@github.com>

Author: dependabot[bot]

intro-nfvis/requirements.txt

@@ -1,4 +1,4 @@
 ciscosparkapi==0.9.2
-requests==2.18.4
+requests==2.20.0
 urllib3==1.22
 webexteamssdk