Remove external HTTP request from hyper crate tests

[goatgoose]

Problem:

To avoid complicating the initial hyper crate PR with a localhost testing framework, a test was added that makes an HTTP request to an external source. This introduces potential flakiness, since requests to external sources aren't reliable.

Solution:

Remove the external HTTP request after localhost testing can be performed.

[jmayclin]

I know that the external HTTP request stuff is a bit tedious, but it is a really nice integration test to have. Maybe if it's a matter of trading off, we could deprecate the "well-known endpoints" integration test and move all of that to a similar integration test relying on s2n-tls-hyper?

[goatgoose]

The purpose of the current external HTTP request is just a sanity check to make sure the hyper crate works at all. I think it does make sense to remove this test after localhost tests are added. However, I do agree that it makes sense to have real network tests, so I opened a separate issue for this: #4837