chore: remove extraneous assert

[abhi7cr]

Description of changes

remove extraneous assert. This was not causing any failures, but is not needed at this point in the code (was added before a code refactor).

Description of how you validated changes

yarn test, manual testing.

../amplify-cli/node_modules/.bin/migrate to-gen-2 execute --from amplify-testref2-dev-8a7e3 --to amplify-mygen2app-ref4-sandbox-f1676df4a6 --debug
✔ Updated Gen 1 auth stack successfully
✔ Updated Gen 2 auth stack successfully
✔ Moved auth resources from Gen 1 to Gen 2 stack successfully
Generated .README file(s) successfully under .amplify/migration/templates directory.

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.