Turn on warnings as errors for Sphinx and pin actions to SHA

Author: melissawm

.github/workflows/check_docs_build.yml

@@ -13,10 +13,12 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8  # v5.0.0
+        with:
+          persist-credentials: false
 
       - name: Set up Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@e797f83bcb11b83ae66e0230d6156d7c80228e7c  # v6.0.0
         with:
           python-version: '3.11'
           cache: 'pip' # caching pip dependencies
@@ -27,4 +29,4 @@ jobs:
       - name: Build documentation
         run: |
           cd docs
-          sphinx-build -b html docs/ docs/_build/html
+          sphinx-build -W -b html docs/ docs/_build/html