ci: make region a parameter to batch script

[awsluja]

Description of changes

This will ensure that region is us-east-1 when requesting a codebuild job so that people who have set a different region locally don't get an error.

Issue #, if available

Description of how you validated changes

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

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