Update selected value stream after deletion
## Summary
After deleting a value stream, we should redirect to a new value stream or the `default` if there are no others.
The following discussion from !42193 should be addressed:
- [ ] @jerasmus started a [discussion](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/42193#note_425260376): (+1 comment)
> @ekigbo this might not be related to this work, so feel free to open a follow-up issue or point me to an existing issue, but when I delete a value stream, the deleted value stream stays selected in the dropdown:
>
> 
issue