Bump prosemirror-markdown from 1.5.1 to 1.5.2

Bumps [prosemirror-markdown](https://github.com/prosemirror/prosemirror-markdown) from 1.5.1 to 1.5.2.
- [Release notes](https://github.com/prosemirror/prosemirror-markdown/releases)
- [Changelog](https://github.com/ProseMirror/prosemirror-markdown/blob/master/CHANGELOG.md)
- [Commits](ProseMirror/prosemirror-markdown@1.5.1...1.5.2)

---
updated-dependencies:
- dependency-name: prosemirror-markdown
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Author: dependabot[bot]