Merge pull request #7388 from docker/dependabot/pip/urllib3-1.25.9

Bump urllib3 from 1.25.7 to 1.25.9

requirements.txt

@@ -24,5 +24,5 @@ requests==2.22.0
 six==1.12.0
 subprocess32==3.5.4; python_version < '3.2'
 texttable==1.6.2
-urllib3==1.25.7; python_version == '3.3'
+urllib3==1.25.9; python_version == '3.3'
 websocket-client==0.57.0