Bump urllib3 from 1.25.7 to 1.25.8

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.25.7 to 1.25.8.
- [Release notes](https://github.com/urllib3/urllib3/releases)
- [Changelog](https://github.com/urllib3/urllib3/blob/main/CHANGES.rst)
- [Commits](urllib3/urllib3@1.25.7...1.25.8)

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

requirements.txt

@@ -15,6 +15,6 @@ pytest==5.3.2
 requests==2.22.0
 simplejson==3.17.0
 six==1.13.0
-urllib3==1.25.7
+urllib3==1.25.8
 wcwidth==0.1.8
 zipp==0.6.0