fix a compile error in iter_any.md

[KANIYONIKA]

The last line of "pub trait Iterator” in iter_any.md is
F: FnMut(Self::Item) -> bool {}
but this results in a compile error.

The reason is that there is a "{}" at the end.

I think that it should be as follows.
F: FnMut(Self::Item) -> bool;

The playground example broken:
https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=8f5be8dc945faa1e70bad4039f132e83

The playground example working:
https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=7c3206888e4931bb77110557231ce723

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @marioidival (or someone else) soon.

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