Bump urllib3 from 1.25.11 to 1.26.0

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.25.11 to 1.26.0.
- [Release notes](https://github.com/urllib3/urllib3/releases)
- [Changelog](https://github.com/urllib3/urllib3/blob/master/CHANGES.rst)
- [Commits](urllib3/urllib3@1.25.11...1.26.0)

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

requirements.txt

@@ -35,7 +35,7 @@ transaction==3.0.0
 translationstring==1.4
 typing==3.7.4.3
 ujson==4.0.1
-urllib3==1.25.11
+urllib3==1.26.0
 venusian==3.0.0
 waitress==1.4.4
 WebOb==1.8.6