Update docutils requirement from <0.20 to <0.21 (#1277)

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

Author: dependabot[bot]

pyproject.toml

@@ -68,7 +68,7 @@ test = [
 docs = [
     # needed because m2r uses deprecated APIs
     # m2r is depended on by sphinxcontrib-openapi
-    "docutils<0.20",
+    "docutils<0.21",
     "ipykernel",
     "jinja2",
     "jupyter_client",