Fix margin on the new/edit project page. (#25885)

Fix margin on the new/edit project page. (#25885)

New/Edit Project page consistent layout. Fix margin on the new/edit
page.

Before:
<img width="1381" alt="image"
src="https://github.com/go-gitea/gitea/assets/80308335/303e128c-0bd0-4289-a395-ff077e33b1c8">
<img width="1392" alt="image"
src="https://github.com/go-gitea/gitea/assets/80308335/d11f7a42-ddf4-4c0a-a1b1-b8cefca9dfa1">

After
<img width="1390" alt="image"
src="https://github.com/go-gitea/gitea/assets/80308335/8ae1a979-9050-4d68-8f5d-9dfaa620c0e8">
<img width="1391" alt="image"
src="https://github.com/go-gitea/gitea/assets/80308335/24a62711-dc0a-4425-bf84-7c1896b9a005">

Co-authored-by: silverwind <me@silverwind.io>