Bump myst-parser from 0.15.2 to 0.16.0 in /docs (GH-2696)

Bumps [myst-parser](https://github.com/executablebooks/MyST-Parser) from 0.15.2 to 0.16.0.
- [Release notes](https://github.com/executablebooks/MyST-Parser/releases)
- [Changelog](https://github.com/executablebooks/MyST-Parser/blob/master/CHANGELOG.md)
- [Commits](executablebooks/MyST-Parser@v0.15.2...v0.16.0)

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

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

docs/requirements.txt

@@ -1,6 +1,6 @@
 # Used by ReadTheDocs; pinned requirements for stability.
 
-myst-parser==0.15.2
+myst-parser==0.16.0
 Sphinx==4.3.1
 sphinxcontrib-programoutput==0.17
 sphinx_copybutton==0.4.0