chore: Ignore variations of amplify_outputs

[vincetran]

• PR title and description conform to Pull Request guidelines.

Issue #, if available: N/A

Description of changes: One of the new integration test files for Email MFA is amplify_outputs_email_or_totp_mfa.json which the current .gitignore doesn't catch

How did you test these changes?
Before: git wants to add amplify_outputs_email_or_totp_mfa.json
After: It doesn't see it

Documentation update required?

• No
• Yes (Please include a PR link for the documentation update)

General Checklist

• Added Unit Tests
• Added Integration Tests
• Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)

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

[mattcreaser]

This is already open as part of #2961