fix: remove square bracket around referred ip lists

[mingkun2020]

Issue #, if available:
#1696

Description of changes:
Removed the code for adding extra square bracket for reference ip list. Before making this change, customer will get sam deploy error when they try to refer a ip list from SSM in attribute IpRangeWhitelist. The deploy error is caused by we adding extra square bracket around a reference ip list.

Description of how you validated changes:
After making the change, I run the sam-translate.py transfer my test sam template to a cloud formation template and then manually deploy the cloud formation template, it works.
Checklist:

• Write/update tests
• make pr passes
• Update documentation
• Verify transformed template deploys and application functions as expected

Examples?

Please reach out in the comments, if you want to add an example. Examples will be
added to sam init through https://github.com/awslabs/aws-sam-cli-app-templates/

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