Zoekt: Rollout is considering offline nodes as well.

Summary

We are not excluding the offline nodes in the SelectionService during the zoekt rollout. It causes issue during rollout because the indices will be attached to the offline node

Steps to reproduce

What is the current bug behavior?

What is the expected correct behavior?

Relevant logs and/or screenshots

Possible fixes

Consider online nodes only here https://gitlab.com/gitlab-org/gitlab/-/blob/e36b393573abb618cbc80d2c18520b2ab25fab09/ee/app/services/search/zoekt/selection_service.rb#L44