fix: update starters and examples to ^1.6.18

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
@mdx-js/mdx (source)	dependencies	patch	^1.6.17 -> ^1.6.18
@mdx-js/react (source)	dependencies	patch	^1.6.17 -> ^1.6.18

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Release Notes

mdx-js/mdx

### [`v1.6.18`](https://togithub.com/mdx-js/mdx/compare/v1.6.17...v1.6.18) [Compare Source](https://togithub.com/mdx-js/mdx/compare/v1.6.17...v1.6.18)

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