Remove hardcoded default credential profile

[sunds]

Summary Remove hard-coded "default" profile for credentials. The AWS SDK will already fall back to default if no profile is selected. This allows the customer to specify alternate profiles in their environment.

Implementation details Remove the hard-coded value and update the unit tests

Testing Unit tests were successfully run on Ubuntu 20.04 with Golang 1.18

New tests cover the changes: Yes. No new lines were added to the codebase.

Description for the changelog Enhancement - Remove hard-coded "default" profile for credentials to allow their specification from the environment with fallback to "default".

Licensing By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.