Update pipfile dependency versions

Includes this vulnerability fix for urllib3:

The urllib3 library 1.26.x before 1.26.4 for Python omits SSL
certificate validation in some cases involving HTTPS to HTTPS
proxies. The initial connection to the HTTPS proxy (if an SSLContext
isn't given via proxy_config) doesn't verify the hostname of the
certificate. This means certificates for different servers that still
validate properly with the default urllib3 SSLContext will be silently
accepted. See CVE-2021-28363.