fix read-the-docs build pipeline (#192)

.readthedocs.yaml

@@ -9,13 +9,13 @@ build:
   os: ubuntu-22.04
   tools:
     python: "3.11"
-  # see https://browniebroke.com/blog/specify-docs-dependency-groups-with-poetry-and-read-the-docs/
   jobs:
     post_create_environment:
     - pip install poetry
-    - poetry config virtualenvs.create false
+    - poetry export --extras docs --without-hashes > doc-requirements.txt
     post_install:
-    - poetry install --extras docs
+    - pip install -r doc-requirements.txt
+    - pip list
 
 python:
   install: