`RefreshPorts` code path doesn't really make sense

[williammartin]

Description

Someone shared this error log for gh cs ssh (used to connect to GitHub codespaces over ssh):

kex_exchange_identification: read: Connection reset by peer
Connection reset by 127.0.0.1 port 65225
tunnel closed: error forwarding port: refresh ports failed: failed to refresh ports: %!w(<nil>)

Looking at the code where this error is returned, there doesn't appear to be any case in which the error will be non-nil:

https://github.com/microsoft/dev-tunnels/blob/845d75c554514d34c6cd80de23ec6d616a674d47/go/tunnels/client.go#L210-L219

I have no opinion on what the message should say. Happy to open a PR with your recommendation.

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Separately, as a minor nit reading this code, it seems like it would be better for the final return on this method to be return nil, since again, no other value is possible.