Unify format for nested non-task lists

What does this MR do?

Removes the specific CSS properties for nested non-task lists in notes.

Are there points in the code the reviewer needs to double check?

No.

Why was this MR needed?

To unify CSS format for nested non-task lists between in notes and in issue/MR description.

Originally, this design for both "notes" and "issue/MR description" was implemented in !2026 (merged) by @rspeicher, but only one was removed in !6487 (merged) by @deckar01 and the other still remains.

Screenshots (if relevant)

before	after

|

See other screenshots on #44384 (closed) for the current CSS formatting in the issue/MR description.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• [n/a] Documentation created/updated
• [n/a] API support added
• [n/a] Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • [n/a] Has been reviewed by Backend
  • [n/a] Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• [n/a] Internationalization required/considered
• [n/a] End-to-end tests pass (package-qa manual pipeline job)

What are the relevant issue numbers?

Closes #44384 (closed)