Quiz for Chapter 20.1 uses syntax no longer used in the book

[timm0e]

• I have searched open and closed issues and pull requests for duplicates, using these search terms:
  • 20.1
  • 19.1
  • unsafe
• I have checked the latest main branch to see if this has already been fixed, in this file:
  • https://github.com/cognitive-engineering-lab/rust-book/blob/main/quizzes/ch19-01-unsafe-rust.toml

URL to the section(s) of the book with this problem:
https://rust-book.cs.brown.edu/ch20-01-unsafe-rust.html

Description of the problem:
The book content uses the the newer &raw syntax to create pointers. The upstream change was done in 2b1ddf4 and merged via #300.
The quiz, however, still uses &v[0] as *const i32 in its example program, which causes confusion since this syntax was never introduced to the reader.

Suggested fix:

• Update the code of the quiz to use the new syntax (See Update quiz for 20.1 to use &raw syntax #374)