Update pyproject.toml

Co-authored-by: Stefanie Molin <[email protected]>

Author: rossbar

pyproject.toml

@@ -41,10 +41,12 @@ file = 'LICENSE.txt'
 Homepage = 'https://numpydoc.readthedocs.io'
 Source = 'https://github.com/numpy/numpydoc/'
 
-[dependency-groups]
+[project.optional-dependencies]
 default = [
     'sphinx>=6',
 ]
+
+[dependency-groups]
 dev = [
     'pre-commit>=3.3',
     "tomli; python_version < '3.11'",