build(deps): Update Rust crate mdbook to v0.4.42

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
mdbook	dependencies	patch	0.4.40 -> 0.4.42

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Release Notes

rust-lang/mdBook (mdbook)

### [`v0.4.42`](https://redirect.github.com/rust-lang/mdBook/blob/HEAD/CHANGELOG.md#mdBook-0442) [Compare Source](https://redirect.github.com/rust-lang/mdBook/compare/v0.4.41...v0.4.42) [v0.4.41...v0.4.42](https://redirect.github.com/rust-lang/mdBook/compare/v0.4.41...v0.4.42) ##### Fixed - Fixed chapter list folding. [#​2473](https://redirect.github.com/rust-lang/mdBook/pull/2473) ### [`v0.4.41`](https://redirect.github.com/rust-lang/mdBook/blob/HEAD/CHANGELOG.md#mdBook-0441) [Compare Source](https://redirect.github.com/rust-lang/mdBook/compare/v0.4.40...v0.4.41) [v0.4.40...v0.4.41](https://redirect.github.com/rust-lang/mdBook/compare/v0.4.40...v0.4.41) **Note:** If you have a custom `index.hbs` theme file, you will need to update it to the latest version. ##### Added - Added preliminary support for Rust 2024 edition. [#​2398](https://redirect.github.com/rust-lang/mdBook/pull/2398) - Added a full example of the remove-emphasis preprocessor. [#​2464](https://redirect.github.com/rust-lang/mdBook/pull/2464) ##### Changed - Adjusted styling of clipboard/play icons. [#​2421](https://redirect.github.com/rust-lang/mdBook/pull/2421) - Updated to handlebars v6. [#​2416](https://redirect.github.com/rust-lang/mdBook/pull/2416) - Attr and section rules now have specific code highlighting. [#​2448](https://redirect.github.com/rust-lang/mdBook/pull/2448) - The sidebar is now loaded from a common file, significantly reducing the book size when there are many chapters. [#​2414](https://redirect.github.com/rust-lang/mdBook/pull/2414) - Updated dependencies. [#​2470](https://redirect.github.com/rust-lang/mdBook/pull/2470) ##### Fixed - Improved theme support when JavaScript is disabled. [#​2454](https://redirect.github.com/rust-lang/mdBook/pull/2454) - Fixed broken themes when localStorage has an invalid theme id. [#​2463](https://redirect.github.com/rust-lang/mdBook/pull/2463) - Adjusted the line-height of superscripts (and footnotes) to avoid adding extra space between lines. [#​2465](https://redirect.github.com/rust-lang/mdBook/pull/2465)

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