Update organization user docs
What does this MR do and why?
Related to gitlab-com/content-sites/handbook!15583 (merged) we will be moving Organization UI to the admin area. Before this decision we had built some organization UI in separate pages and had them documented at https://docs.gitlab.com/user/organization/. This MR removes a lot of this documentation for now to avoid confusion.
MR acceptance checklist
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Edited by Peter Hegman