ci: fix docs ci job (#239)

Author: henryiii

.readthedocs.yaml

@@ -15,4 +15,4 @@ build:
     - asdf global uv latest
     - uv venv
     - uv pip install .[docs]
-    - .venv/bin/python -m sphinx -T -b html -d docs/_build/doctrees -D language=en docs $READTHEDOCS_OUTPUT/html
+    - . .venv/bin/activate && sphinx-build -T -b html -d docs/_build/doctrees -D language=en docs $READTHEDOCS_OUTPUT/html