Remove long disabled integration test

[d-ronnqvist]

Bug/issue #, if applicable:

Summary

This removes an integration test—and code only used by that test—that's been disabled since the initial open source release of Swift-DocC.

The original reason for disabling this test was that it makes real network requests to a local preview server. This behavior made the test unsuitable for running in a CI environment because its effect couldn't be isolated. Since the purpose of the test is to test real network request to the local preview server, there's no reasonable expectation for reenabling this test.

Dependencies

None

Testing

None.

Checklist

Make sure you check off the following items. If they cannot be completed, provide a reason.

• Added tests
• Ran the ./bin/test script and it succeeded
• Updated documentation if necessary

[mayaepps]

Can this test be rewritten without the network requests? From the comments it seems like the test was meant to ensure the preview request recovered after a failed convert attempt, which seems like behavior it would still be nice to test.