[clang-tools-extra] [clang-tidy] Fix documentation in `modernize-avoid-c-style-cast` (PR #171413)

[Islam Imad via cfe-commits]

Islam-Imad wrote:

> Related discussion: [#171058 (comment)](https://github.com/llvm/llvm-project/pull/171058#discussion_r2602100364)

Sorry about that 😐 
but I only moved the requested lines from past review 

https://github.com/llvm/llvm-project/pull/171413