Add example AWS access keys to allowlist

[risto-liftoff]

Description:

Hi, I'm working on introducing gitleaks into my company, and gitleaks flagged an AWS access key that is just meant for examples and is used in AWS documentation, e.g., https://docs.aws.amazon.com/STS/latest/APIReference/API_GetAccessKeyInfo.html.

Checklist:

• [x] Does your PR pass tests?
• [ ] Have you written new tests for your changes? No, I don't think it's necessary for so a simple a change.
• [x] Have you lint your code locally prior to submission?