Fix Resource Limit Issue with Deployment to DMZ

[Matthew-Grayson]

🗣 Description

Mark aws-sdk v2 and its associated dependencies as dev dependencies.

💭 Motivation and context

This addresses a deployment issue related to the unzipped lambda package being too large.
Closes issue #511
aws-sdk version 2 is preinstalled in the Node 16 lambda image. By marking it as a dev dependency, we reduce the size of the Scan Execution lambda.

See more about preinstalled packages here.

🧪 Testing

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• Changes are limited to a single goal - eschew scope creep!
• All future TODOs are captured in issues, which are referenced
  in code comments.
• All relevant type-of-change labels have been added.
• I have read the CONTRIBUTING document.
• These code changes follow cisagov code standards.
• All relevant repo and/or project documentation has been updated
  to reflect the changes in this PR.
• Tests have been added and/or modified to cover the changes in this PR.
• All new and existing tests pass.

✅ Pre-merge checklist

• Revert dependencies to default branches.
• Finalize version.

✅ Post-merge checklist

• Create a release.