Clarify `ManagerIdentity` in `docs/ownership.md`

[opeik]

Hi there,

At the moment, the docs state:

Once it is available in OSS v1.29, the controller will be able to coordinate with other users via the ManagerIdentity field of a Worker Deployment. This runbook will be updated when that is available and implemented by the controller.

It looks like temporalio/server:1.29 is already out. Is this documentation still relevant?

[carlydf]

Thanks for pointing this out! The server-side capability to use ManagerIdentity instead of this metadata hack is available, but the Controller has not implemented it yet. I will update the docs to make that clear.

Once the controller code changes to use the more elegant ManagerIdentity method of ownership coordination, I will also update the doc (and point it out in the release notes)