Update urllib3 to 1.25.8

[pyup-bot]

This PR updates urllib3 from 1.25.6 to 1.25.8.

Changelog

1.25.8

-------------------

* Drop support for EOL Python 3.4 (Pull 1774)

* Optimize _encode_invalid_chars (Pull 1787)

1.25.7

-------------------

* Preserve ``chunked`` parameter on retries (Pull 1715, Pull 1734)

* Allow unset ``SERVER_SOFTWARE`` in App Engine (Pull 1704, Issue 1470)

* Fix issue where URL fragment was sent within the request target. (Pull 1732)

* Fix issue where an empty query section in a URL would fail to parse. (Pull 1732)

* Remove TLS 1.3 support in SecureTransport due to Apple removing support (Pull 1703)

Links

• PyPI: https://pypi.org/project/urllib3
• Changelog: https://pyup.io/changelogs/urllib3/
• Docs: https://urllib3.readthedocs.io/

[pyup-bot]

Closing this in favor of #231