[REF] Update CONTRIBUTING.md

[Remi-Gau]

Refactor as similar content is now in the bids/.github repo

All Submissions:

• [ ] Have you followed the guidelines in our Contributing document?
• [ ] Have you checked to ensure there aren't other open Pull Requests for the same update/change?

New Feature Submissions:

1. [ ] Does your submission pass tests?
2. [ ] Have you lint your code locally prior to submission?

Changes to Core Features:

• [ ] Have you added an explanation of what your changes do and why you'd like us to include them?
• [ ] Have you written new tests for your core changes, as applicable?
• [ ] Have you successfully ran tests with your changes locally?