Follow-up from "Remove namespace selector"
The following discussion from !13515 should be addressed:
- [ ] @vvempati started a [discussion](https://gitlab.com/gitlab-org/customers-gitlab-com/-/merge_requests/13515#note_2838995969): (+2 comments)
> **question:** Do we need to pass this as an array now that we don't support namespace selection on SaaS purchase flow? Can we instead just send `current_namespace` here and update the frontend logic accordingly so we don't need to access the first item in the array to get the selected group in the following blocks:
>
> ```
> initializeSelectedGroup() {
> const [selectedGroup] = this.groups || [];
> ...
> }
> ```
>
> ```
> groups() {
> return (
> // Return the single pre-selected namespace
> this.namespaces ?? []
> );
> },
> ```
>
> ```suggestion:-0+0
> current_namespace: @current_namespace.to_json,
> ```
issue