Update myst-parser requirement from ~=1.0.0 to >=1.0,<2.1 in /package

Updates the requirements on [myst-parser](https://github.com/executablebooks/MyST-Parser) to permit the latest version.
- [Release notes](https://github.com/executablebooks/MyST-Parser/releases)
- [Changelog](https://github.com/executablebooks/MyST-Parser/blob/master/CHANGELOG.md)
- [Commits](executablebooks/MyST-Parser@v1.0.0...v2.0.0)

---
updated-dependencies:
- dependency-name: myst-parser
  dependency-type: direct:development
...

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

package/setup.py

@@ -56,7 +56,7 @@
             "sphinx_copybutton==0.3.1",
             "sphinx-notfound-page",
             "sphinx_rtd_theme==1.2.0",
-            "myst-parser~=1.0.0",
+            "myst-parser>=1.0,<2.1",
         ],
     },
 )