chore: fix RTD build with Poetry 1.8 (#945)

.readthedocs.yml

@@ -12,12 +12,10 @@ build:
   jobs:
     post_create_environment:
       # Install poetry
-      - pip install poetry==1.7.1
-      # Tell poetry to not use a virtual environment
-      - poetry config virtualenvs.create false
+      - python -m pip install poetry
     post_install:
-      # Install dependencies
-      - poetry install --with docs
+      # Install dependencies, reusing RTD virtualenv
+      - VIRTUAL_ENV=$READTHEDOCS_VIRTUALENV_PATH poetry install --with docs
 
 # Build documentation in the docs directory with Sphinx
 sphinx: