Bump urllib3 from 1.25.8 to 1.25.9

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.25.8 to 1.25.9.
- [Release notes](https://github.com/urllib3/urllib3/releases)
- [Changelog](https://github.com/urllib3/urllib3/blob/master/CHANGES.rst)
- [Commits](urllib3/urllib3@1.25.8...1.25.9)

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

requirements.txt

@@ -35,7 +35,7 @@ transaction==3.0.0
 translationstring==1.3
 typing==3.7.4.1
 ujson==2.0.3
-urllib3==1.25.8
+urllib3==1.25.9
 venusian==3.0.0
 waitress==1.4.3
 WebOb==1.8.6