Fix ReadTheDocs config for Poetry (#1663)

.readthedocs.yaml

@@ -3,10 +3,16 @@ version: 2
 sphinx:
   configuration: docs/conf.py
 
-python:
-  version: 3.7
-  install:
-    - method: pip
-      path: .
-      extra_requirements:
-        - docs
+build:
+  os: "ubuntu-22.04"
+  tools:
+    python: "3.8"
+  jobs:
+    post_create_environment:
+      # Install poetry
+      - pip install poetry
+      # Tell poetry to not use a virtual environment
+      - poetry config virtualenvs.create false
+    post_install:
+      # Install dependencies with 'docs' dependency group
+      - poetry install --with docs