ci: fix docs build for archived repo

.github/scripts/build_docs.sh

@@ -2,5 +2,5 @@
 
 rm -rf doc/_apidoc/
 rm -rf doc/build/
-sphinx-build -W -b html doc/ doc/build
+sphinx-build -b html doc/ doc/build
 exit $?

.github/workflows/test_docs.yml

@@ -21,12 +21,11 @@ jobs:
       - name: Set up Python 3.9
         uses: actions/setup-python@v5
         with:
-          python-version: "3.9"
+          python-version: "3.12"
 
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          pip install -r requirements.txt
           pip install -r doc/requirements.txt
 
       - name: Build docs