Fix pip command (#342)

Sorry again. Look like it come from the yaml. If still not working after
that I will just remove the condition.
Cannot test it in local and cannot push directly to master.

.readthedocs.yaml

@@ -8,7 +8,8 @@ build:
     post_create_environment:
       # Install poetry
       # https://python-poetry.org/docs/#installing-manually
-      - pip install poetry<3.0.0
+      - >-
+        pip install 'poetry<3.0.0'
     post_install:
       # Install dependencies with 'docs' dependency group
       # https://python-poetry.org/docs/managing-dependencies/#dependency-groups