Fix: Use python 3.8 for docs to match the Jenkins verification.

Once this is confirmed to be working, we can ask the teams to migrate
docs to 3.11

Signed-off-by: Jessica Wagantall <jwagantall@linuxfoundation.org>

.github/workflows/compose-rtdv3-verify.yaml

@@ -74,7 +74,7 @@ jobs:
       - uses: actions/setup-python@v4
         id: setup-python
         with:
-          python-version: "3.11"
+          python-version: "3.8"
       - name: Verify If readthedocs Config exists
         run: |
           echo "Verifying if readthedocs.yaml config file exists"