Update dependency Markdown to <3.7

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
Markdown (changelog)	<3.6 -> <3.7

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Release Notes

Python-Markdown/markdown (Markdown)

### [`v3.6`](https://togithub.com/Python-Markdown/markdown/compare/3.5.2...3.6) [Compare Source](https://togithub.com/Python-Markdown/markdown/compare/3.5.2...3.6)

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Configuration

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