Tests fail - timeout because https2.golang.org doesn't exist

[Sinc63]

Environment

• Elixir & Erlang/OTP versions (elixir --version):
• Operating system:

Current behavior

Many tests in kadabra_test and a couple in connection_test fail because the URI used is no longer valid.

Include code samples, errors and stacktraces if appropriate.

Expected behavior

Tests should pass in the base software, to enable them to pass in a fork.