Bump markdown-it-testgen from 0.1.4 to 0.1.6

Bumps [markdown-it-testgen](https://github.com/markdown-it/markdown-it-testgen) from 0.1.4 to 0.1.6.
- [Release notes](https://github.com/markdown-it/markdown-it-testgen/releases)
- [Changelog](https://github.com/markdown-it/markdown-it-testgen/blob/master/CHANGELOG.md)
- [Commits](https://github.com/markdown-it/markdown-it-testgen/compare/0.1.4...0.1.6

)

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