Update various team compositions

[kiwitaco]

Small adjustments for members leaving and joining teams

[greptile-apps]

Greptile Summary

Updates team memberships and Writing Team co-leadership.

Confidence Score: 5/5

The documentation-only roster updates appear safe to merge.

No concrete formatting, link, build, or repository-rule failures were found.

_{Reviews (1): Last reviewed commit: "Update about-us.md" | Re-trigger Greptile}