Delete app/views/projects/blob/_new_dir.html.haml and any other related code
<!--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=417131)
</details>
<!--IssueSummary end-->
The following discussion from !125126 should be addressed:
- [ ] @annabeldunstone started a [discussion](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/125126#note_1458898780): (+5 comments)
> @markrian Is this file still being used? I see we have a [Vue version](https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/assets/javascripts/ide/components/new_dropdown/modal.vue) as well :thinking:
issue