review: use locked uv for docs

Author: pjhartzell

.github/workflows/continuous-integration.yml

@@ -68,6 +68,6 @@ jobs:
       - uses: actions/checkout@v5
       - uses: astral-sh/setup-uv@v6
       - name: Install
-        run: uv sync --only-group docs
+        run: uv sync --locked --only-group docs
       - name: Make docs
         run: cd docs && uv run make html