Use sentence case for edit page, remove hr

What does this MR do and why?

• Use sentence case across Edit pages
• Remove hr

What does this MR not do?

Fix the breadcrumbs

Screenshots or screen recordings

Example from edit milestone page:

Before	After

How to set up and validate locally

Links

• ✂️ UX Paper Cuts 17.1 → Improve Wiki Experience (#452225 - closed)