Combine redundant sections

[rbowen]

Description

Combines redundant sections in the CONTRIBUTING doc.

Type of Change

• Content update/revision
• Structure/organization improvement

Motivation and Context

Onboarding new contributors is a first step in community building. Making this as easy as possible leads to more first-contribution success.

Areas Affected

CONTRIBUTING.md

Checklist

• [ x] I have read the CONTRIBUTING document
• [ x] My changes follow the project's documentation style
• I have tested the documentation locally using mkdocs serve
• [ x] Links in the documentation are valid and working
• Images/diagrams are properly sized and formatted
• All new and existing tests pass

Additional Notes

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[yonib05]

Thank you so much for your contribution!