[Docs] Explicit python 3.12 for sphinx and imghdr (#2030)

Author: danhoeflinger

.github/workflows/ci-docs.yml

@@ -33,7 +33,8 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
         with:
-          python-version: '3.x'
+          # Set the python version to 3.12 to keep imghdr for sphinx. Could upgrade sphinx to 6.2 to use 3.x version.
+          python-version: '3.12'
       - name: Install prerequisites
         run: |
           echo GITHUB_SHA_SHORT=${GITHUB_SHA::8} >> $GITHUB_ENV