Add changelog for IMDSv2 fix

[rbbarad]

Description

Adds a changelog for the fix in https://github.com/aws/aws-toolkit-azure-devops/pull/535

Checklist

• [x] I have read the README document
• [x] I have read the CONTRIBUTING document
• [x] My code follows the code style of this project
• [ ] I have added tests to cover my changes
• [x] A short description of the change has been added to the changelog using the script npm run newChange

License

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.