CUMULUS-3737: Cherry-picks CUMULUS-3779. Reverts CL to Unreleased

[paulpilone]

Summary: Summary of changes

Addresses CUMULUS-3737: Release 18.3

Changes

• Adds https://github.com/nasa/cumulus/pull/3689 to 18.3.x to support stripping of aws-sdk v3 from packages
• Reverts 18.3.0 CL section to Unreleased since we're skipping that broken release.

PR Checklist

• [x] Update CHANGELOG
• [ ] Unit tests
• [ ] Ad-hoc testing - Deploy changes and test manually
• [ ] Integration tests

[paulpilone]

I need to do some work on the release 18.3.x branch before we can make this change.