test: convert .then to async/await for batchUploader tests

[jaissica12]

Instructions

1. PR target branch should be against development
2. PR title name should follow this format: https://github.com/mParticle/mparticle-workflows/blob/main/.github/workflows/pr-title-check.yml
3. PR branch prefix should follow this format: https://github.com/mParticle/mparticle-workflows/blob/main/.github/workflows/pr-branch-check-name.yml

Summary

• Updated all occurrences of .then to async/await for batch uploader tests

Testing Plan

• Was this tested locally? If not, explain why.
• {explain how this has been tested, and what, if any, additional testing should be done}

Reference Issue (For mParticle employees only. Ignore if you are an outside contributor)

• Closes https://rokt.atlassian.net/browse/SDKE-338

[sonarqubecloud]

Quality Gate failed

Failed conditions
22.7% Duplication on New Code (required ≤ 3%)

See analysis details on SonarQube Cloud