[clang-tools-extra] [clang-tidy][NFC] Fix formatting issue in `unsafe-functions.rst` (PR #168722)

[via cfe-commits]

zeyi2 wrote:

> fix everything once we land it.

I think maybe I can convert this into a draft for fixing all the issues before we land the linter?

https://github.com/llvm/llvm-project/pull/168722