readthedocs: use latest recommendations for poetry install

.readthedocs.yml

@@ -20,12 +20,10 @@ build:
       # Install poetry
       # https://python-poetry.org/docs/#installing-manually
       - pip install poetry
-      # Tell poetry to not use a virtual environment
-      - poetry config virtualenvs.create false
     post_install:
       # VIRTUAL_ENV needs to be set manually for now.
       # See https://github.com/readthedocs/readthedocs.org/pull/11152/
-      - cd doc && poetry install
+      - cd doc && VIRTUAL_ENV=$READTHEDOCS_VIRTUALENV_PATH poetry install
 
 # Build documentation in the "docs/" directory with Sphinx
 sphinx: