Update documentation of cdk-high-contrast (since last major rework for version 9)

[biolauri]

Documentation Feedback

The current paragraph on the cdk-high-contrast hasn't been update on the last major rework in #17378. It still states that it uses a media query and I would like to have some information on its dependencies, which is currently located in JSDoc only.

Currently, the example isn't working, as described in #18147

Affected documentation page: https://next.material.angular.io/cdk/a11y/overview#targeting-high-contrast-users

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