fix e2e migration test broken by #11790

[Amplifiyer]

Description of changes

With a change in prompt string, the old test's expected prompt was not compatible.
#11790 changed the prompt

- Enter your Private Key for your OAuth flow:
+ Enter your Private Key for your OAuth flow (entire key without line breaks):

This PR changes the expected prompt to the common string Enter your Private Key for your OAuth flow for migration e2e tests.

Description of how you validated changes

cloud e2e tests
Failed -> Passed with this change

Checklist

• PR description included
• yarn test passes
• Tests are changed or added
• Relevant documentation is changed or added (and PR referenced)
• New AWS SDK calls or CloudFormation actions have been added to relevant test and service IAM policies
• Pull request labels are added

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

[sobolk]

thank you