Incorrect error with `axiom dataset list` for bad deployment alias

When using an alias to that is no longer valid the `axiom dataset list`
command returns an error of the form:

```bash
$ AXIOM_DEPLOYMENT=bogus-no-longer-valid-env axiom dataset list
Error: cannot decode response with unknown content type
```

This can be cross-checked with `axiom auth status` which will show valid and non-valid auth tokens by alias

Reproduce the problem with AXIOM_DEPLOYMENT=bogus-no-longer-valid-env axiom dataset list, then compare its response handling with axiom auth status for the same alias. Trace the dataset list command's handling of an invalid deployment response; done means the command reports a useful invalid-alias or authentication error instead of "cannot decode response with unknown content type."

Written by the indexing model from the issue text.