Update ca1507.md

[Youssef1313]

The usage of nameof really doesn't add any readability in my opinion. It's just good to use it for maintainability, specially, when renaming arguments.

throw new ArgumentNullException(nameof(arg));
throw new ArgumentNullException("arg");

Both lines are as same readable.

[PRMerger15]

@Youssef1313 : Thanks for your contribution! The author(s) have been notified to review your proposed change.