[clang] [clang][docs] fix rendering of `$`-prefixed options (PR #119249)

[Carlo Cabrera via cfe-commits]

carlocab wrote:

No worries, I missed it too. For future reference, it might be useful to check the rich diff too:

<img width="306" alt="Screenshot 2024-12-10 at 3 23 35 AM" src="https://github.com/user-attachments/assets/003082f8-1135-4be2-996a-2cde6691f61a">


https://github.com/llvm/llvm-project/pull/119249