fix: Update sphinx-autoapi to version 3.x

pyproject.toml

@@ -50,7 +50,7 @@ flake8 = "^3.9"
 # documentation
 # NOTE: when changing these, update docs-requirements.txt
 sphinx = "^4.2"
-sphinx-autoapi = "^2.0.1"
+sphinx-autoapi = "^3.0.0"
 sphinx-rtd-theme = "^1.0.0"
 sphinxcontrib-openapi = "^0.8.1"
 jsonschema = ">=4.10.0,<4.18.0"  # newer versions break sphinxcontrib-openapi