Updated the code comment to explain the correct type of Future result.
Updated the code comment to explain the correct type of Future result.

Motivation:

This is done because when using Xcode and option + Click on a function you get a help overview inline to see more information and the messaging was incorrect. This helps developers in the future who want to rely on docs via Xcode.

Modification:

Correct the docs

Result:

More correct docs.
apple/swift-nio,apple/swift-nio,apple/swift-nio,apple/swift-nio,apple/swift-nio