Bump myst-parser from 3.0.1 to 4.0.0 in /docs

Bumps [myst-parser](https://github.com/executablebooks/MyST-Parser) from 3.0.1 to 4.0.0.
- [Release notes](https://github.com/executablebooks/MyST-Parser/releases)
- [Changelog](https://github.com/executablebooks/MyST-Parser/blob/master/CHANGELOG.md)
- [Commits](executablebooks/MyST-Parser@v3.0.1...v4.0.0)

---
updated-dependencies:
- dependency-name: myst-parser
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

docs/requirements.txt

@@ -14,7 +14,7 @@ charset-normalizer==3.2.0
     # via requests
 defusedxml==0.7.1
     # via sphinxcontrib-datatemplates
-docutils==0.18.1
+docutils==0.20.1
     # via
     #   myst-parser
     #   sphinx
@@ -35,11 +35,11 @@ markdown-it-py==3.0.0
     #   myst-parser
 markupsafe==2.1.3
     # via jinja2
-mdit-py-plugins==0.4.0
+mdit-py-plugins==0.4.1
     # via myst-parser
 mdurl==0.1.2
     # via markdown-it-py
-myst-parser==3.0.1
+myst-parser==4.0.0
     # via -r requirements.in
 openpyxl==3.1.3
     # via -r requirements.in