Allow docutils 0.18

Updated upstream in sphinx-doc/sphinx#10164, released as part of the 5.0.0 release: https://www.sphinx-doc.org/en/master/changes.html

recipe/meta.yaml

@@ -9,7 +9,7 @@ source:
   sha256: 464d9c1bd5613bcebe76b46658763f3f3dbb184da7406e632a84596d3cd8ee90
 
 build:
-  number: 0
+  number: 1
   noarch: python
   script: {{ PYTHON }} -m pip install . -vv
   entry_points:
@@ -27,7 +27,7 @@ requirements:
     - python >=3.6
     - alabaster >=0.7,<0.8
     - babel >=1.3
-    - docutils >=0.14,<0.18
+    - docutils >=0.14,<0.19
     - imagesize
     - importlib-metadata >=4.4
     - jinja2 >=2.3