Bump urllib3 from 1.25.7 to 1.26.5

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.25.7 to 1.26.5.
- [Release notes](https://github.com/urllib3/urllib3/releases)
- [Changelog](https://github.com/urllib3/urllib3/blob/main/CHANGES.rst)
- [Commits](urllib3/urllib3@1.25.7...1.26.5)

---
updated-dependencies:
- dependency-name: urllib3
  dependency-type: direct:production
...

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

requirements.txt

@@ -7,7 +7,7 @@ promise==2.2.1
 python-igraph==0.7.1.post6
 requests==2.22.0
 six==1.13.0
-urllib3==1.25.7
+urllib3==1.26.5
 matplotlib==3.2.1
 chord==0.0.11
 sklearn==0.0