Updated CONTRIBUTING.md Section 1.7

[gdkoo]

Fixes #6450

What changes did you make?

• Removed duplicate instance of Section 1.7 in CONTRIBUTING.md

Why did you make the changes (we will use this info to test)?

• For Reviewers: Do not review changes locally, rather, review changes at https://github.com/gdkoo/website/blob/update-contributing.md-section-1.7-6450/CONTRIBUTING.md
• To clarify onboarding material and reduce potential confusion from attendees

Screenshots of Proposed Changes Of The Website (if any, please do not screen shot code changes)

Changes were made to Github guide for developers. No changes to website.

[github-actions]

Want to review this pull request? Take a look at this documentation for a step by step guide!

From your project repository, check out a new branch and test the changes.

git checkout -b gdkoo-update-contributing.md-section-1.7-6450 gh-pages
git pull https://github.com/gdkoo/website.git update-contributing.md-section-1.7-6450

---

Note that CONTRIBUTING.md cannot previewed locally; rather it should be previewed at this URL:

https://github.com/gdkoo/website/blob/update-contributing.md-section-1.7-6450/CONTRIBUTING.md  

[roslynwythe]

Very nice @gdkoo. You made a clean, correct code change, setup the pull request branches correctly, described your work and provided a preview URL for the convenience of reviewers. Thank you!

[ajb176]

Changes look to be exactly as requested, nice work @gdkoo