Remove unused file

What does this MR do and why?

• Removes app/views/projects/blob/_new_dir.html.haml as this modal has been converted to vue in app/assets/javascripts/repository/components/new_directory_modal.vue (!142051 (comment 1731888564))

Links

✂️ UX Paper Cuts 16.9 → Pajamas Migrations (#430246 - closed)