Use released Docutils 0.19 on CI

.github/workflows/main.yml

@@ -21,7 +21,7 @@ jobs:
         - python: "3.10"
           docutils: du18
         - python: "3.10"
-          docutils: du19pre
+          docutils: du19
         - python: "3.11-dev"
           docutils: py311
 

tox.ini

@@ -37,11 +37,6 @@ commands =
     python -m pip install "git+https://repo.or.cz/docutils.git#subdirectory=docutils"
     {[testenv]commands}
 
-[testenv:du19pre]
-commands =
-    python -m pip install --pre "docutils==0.19.*"
-    {[testenv]commands}
-
 [testenv:flake8]
 basepython = python3
 description =