Requests: Upgrade Urllib3 Version

[MarianG]

I just encountered a problem, when I tried to run a regular script, because the dependencies for requests are a bit outdated. In your setup.py you still require urllib3 with a version limitation: 'urllib3>=1.21.1,<1.26,!=1.25.0,!=1.25.1'.
My Problem was that the current available version 1.26 is obviously not valid and my pip command fails within the installation of the requests package.

Expected Result

Installation of package completes as usual.

Actual Result

ERROR: Could not find a version that satisfies the requirement urllib3!=1.25.0,!=1.25.1,<1.26,>=1.21.1

Reproduction Steps

   pip install urllib3

   pip install requests

[nateprewitt]

This will be resolved tomorrow in #5651.

[nateprewitt]

Requests 2.25.0 should now be released.