[Issue 13118] Allow non-`@nogc` stuff in `@nogc` function contracts

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=13118

--- Comment #9 from yebblies <yebblies at gmail.com> ---
(In reply to Denis Shelomovskij from comment #8)
> 
> `assert` is here just because it is where `format` is called. I'm talking
> about `format`.

You're right, I missed that, but it is addressed in the other comments.

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