Fix rustfmt failing to format closure block body with comment

[topecongiro]

An example taken from rls/src/build/cargo.rs:

            let modified = args.iter()
                .map(|a| {
                    // Emitting only dep-info is possible only for final crate type, as
                    // as others may emit required metadata for dependent crate types
                    if a.starts_with("--emit") && is_final_crate_type && !self.workspace_mode {
                        "--emit=dep-info"
                    } else { a }
                })
                .collect::<Vec<_>>();

rustfmt fails to format the above snippet. This PR fixes it.

[nrc]

Thank you!