Docs: "Move project into a group" doc is gone

From this community feedback: https://docs.gitlab.com/ee/user/project/index.html#comment-3927659395:

Hey! Came here from https://docs.gitlab.com/ee/user/group/#transfer-projects-into-groups to see information about transferring project into a group, and didn't find it.

@axil @victorwu any ideas what happened with this part of the doc? I'm pretty sure I've seen this info there before.

From a doc search I found https://docs.gitlab.com/ee/user/project/settings/#transferring-an-existing-project-into-another-namespace but it's quite not exactly the same. The operation is, but the reasoning may differ.