Align the parent dropdowns/names when selecting groups for migration
<!--IssueSummary start-->
<details>
<summary>
Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards.
</summary>
- [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=340605)
</details>
<!--IssueSummary end-->
Follow-up from "Allow groups to be re-imported":
The following discussion from !68055 should be addressed:
- [ ] @jiaan started a [discussion](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/68055#note_671319742): (+1 comment)
> **Nitpick (non-blocking):** This is a really minor UI nitpick, but WDYT about aligning rows parent dropdown width so that they're all the same?
>
> 
issue