Update Rust crate mdbook to ^0.4.32

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
mdbook	dependencies	patch	^0.4.31 -> ^0.4.32

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Release Notes

rust-lang/mdBook (mdbook)

### [`v0.4.32`](https://togithub.com/rust-lang/mdBook/blob/HEAD/CHANGELOG.md#mdBook-0432) [Compare Source](https://togithub.com/rust-lang/mdBook/compare/v0.4.31...v0.4.32) [v0.4.31...v0.4.32](https://togithub.com/rust-lang/mdBook/compare/v0.4.31...v0.4.32) ##### Fixed - Fixed theme-color meta tag not syncing with the theme. [#​2118](https://togithub.com/rust-lang/mdBook/pull/2118) ##### Changed - Updated all dependencies. [#​2121](https://togithub.com/rust-lang/mdBook/pull/2121) [#​2122](https://togithub.com/rust-lang/mdBook/pull/2122) [#​2123](https://togithub.com/rust-lang/mdBook/pull/2123) [#​2124](https://togithub.com/rust-lang/mdBook/pull/2124) [#​2125](https://togithub.com/rust-lang/mdBook/pull/2125) [#​2126](https://togithub.com/rust-lang/mdBook/pull/2126)

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