docs: remove CoC reference from contributing md

[mlaurencin]

Given that the CoC document is up to date in the .github repository, this reference should be removed so that the .github CoC is the only one visible and mentioned in this repository.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 54.80%. Comparing base (7b18a69) to head (73e8245).
⚠️ Report is 101 commits behind head on main.

❗ There is a different number of reports uploaded between BASE (7b18a69) and HEAD (73e8245). Click for more details.

HEAD has 37 uploads less than BASE

Flag	BASE (7b18a69)	HEAD (73e8245)
	40	3

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #1295       +/-   ##
===========================================
- Coverage   73.96%   54.80%   -19.17%     
===========================================
  Files          21       23        +2     
  Lines         776      770        -6     
  Branches      150      177       +27     
===========================================
- Hits          574      422      -152     
- Misses        148      313      +165     
+ Partials       54       35       -19     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.