Downgrade release-docs action Py version to 3.11

Temporary downgrade the Python version to 3.11 in
the release-docs workflow to avoid a Pydantic
error when importing spacy.

TypeError: ForwardRef._evaluate() missing 1
required keyword-only argument: 'recursive_guard'

.github/workflows/release-docs.yml

@@ -15,7 +15,7 @@ jobs:
       - name: Build River
         uses: ./.github/actions/install-env
         with:
-          python-version: "3.12"
+          python-version: "3.11"
 
       - name: Install extra Ubuntu dependencies
         run: sudo apt-get install graphviz pandoc