Change SERVICENOW_ID references to ASSESSMENT_ID

[nickviola]

🗣 Description

This PR resolves #30 and changes all references of SERVICENOW_ID to ASSESSMENT_ID in this project.

💭 Motivation and context

Leadership has requested these changes be implemented to clarify ID references.

🧪 Testing

Run the script as usage suggests and verify output references are replaced.

✅ Pre-approval checklist

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

✅ Pre-merge checklist

• [x] Revert dependencies to default branches.
• [x] Finalize version.

✅ Post-merge checklist

• [ ] Create a release.

[coveralls]

Pull Request Test Coverage Report for Build 6176327274

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 0.0%

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Totals
Change from base Build 6174735645:	0.0%
Covered Lines:	0
Relevant Lines:	0

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💛 - Coveralls