Bump urllib3 from 1.24.2 to 1.25.7

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.24.2 to 1.25.7.
- [Release notes](https://github.com/urllib3/urllib3/releases)
- [Changelog](https://github.com/urllib3/urllib3/blob/master/CHANGES.rst)
- [Commits](urllib3/urllib3@1.24.2...1.25.7)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements.txt

@@ -30,6 +30,6 @@ requests==2.20.4
 SecretStorage==2.3.1
 simplejson==3.13.2
 six==1.11.0
-urllib3==1.24.2
+urllib3==1.25.7
 websocket-client==0.57.0
 xmltodict==0.11.0