chore: add sync-repo-settings.yaml to exclude unit-test for Python 3.7

[chelsea-lin]

This change adds the sync-repo-settings.yaml setting to exclude unit-test for Python 3.7, which is going to be dropped by #286.

• Make sure to open an issue as a bug/issue before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
• Ensure the tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)

Fixes #<issue_number_goes_here> 🦕