fix(deps): update dependency @marp-team/marpit to v3.1.1

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
@marp-team/marpit (source)	3.1.0 -> 3.1.1

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Release Notes

marp-team/marpit (@​marp-team/marpit)

### [`v3.1.1`](https://togithub.com/marp-team/marpit/blob/HEAD/CHANGELOG.md#v311---2024-08-31) [Compare Source](https://togithub.com/marp-team/marpit/compare/v3.1.0...v3.1.1) ##### Fixed - Update type definition to add `cssNesting` constructor option ([#​401](https://togithub.com/marp-team/marpit/pull/401))

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