Bump remark-gfm from 3.0.1 to 4.0.0

Bumps [remark-gfm](https://github.com/remarkjs/remark-gfm) from 3.0.1 to 4.0.0.
- [Release notes](https://github.com/remarkjs/remark-gfm/releases)
- [Commits](remarkjs/remark-gfm@3.0.1...4.0.0)

---
updated-dependencies:
- dependency-name: remark-gfm
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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