Update dev dependency @types/tunnel

[mikeharder]

@daviwil: Note the move from dependencies to devDependencies in core-http. I assume having an @types package in regular dependencies is always a mistake?

[daviwil]

I think the only time it isn't a mistake is if one of those types is being re-exported from the public interface of one of our libraries. I just ran into an issue like that with having @azure/abort-controller as a devDependency of @azure/core-auth. The TypeScript compiler complains about not having access to the AbortSignalLike type that I re-export from @azure/core-auth's public interface. Changing it to a dependency solves the problem.

[daviwil]

That said, moving @types/tunnel to a devDependency in this PR is the right thing to do as far as I can tell :)

[mikeharder]

Follow-up:

• [core-http] Handle case where proxySettings.host does not contain a valid hostname ([core-http] Handle case where proxySettings.host does not contain a valid hostname #4544)