Fix or document sso profile credential loading for aws-sdk-rust

[rchowell]

Describe the bug

awslabs/aws-sdk-rust#741

We could also mitigate this with some additional documentation.

To Reproduce

With a recent version of the aws-cli,

aws configure sso

Then using daft with the older rust sdk will fail to load credentials with a "file not found" issue which is a somewhat opaque error. The fix is to remove the sso_session field from a profile, then move all fields from the sso_session entry to the profile entry.

Expected behavior

No response

Component(s)

Documentation

Additional context

awslabs/aws-sdk-rust#741