temp: build: compile python requirements with 3.8, not 3.11

We haven't quite dropped 3.8 support yet, so we can't use these
workflows if they're compiling with 3.11

Revert this commit when we drop 3.8 support.

WIP: how do we tell the upgrade requirements workflow to use 3.8?

.github/workflows/compile-python-requirements.yml

@@ -26,7 +26,7 @@ jobs:
       - name: Set up Python environment
         uses: actions/setup-python@v5
         with:
-          python-version: "3.11"
+          python-version: "3.8"
 
       - name: Run make compile-requirements
         env:

.github/workflows/upgrade-one-python-dependency.yml

@@ -39,7 +39,7 @@ jobs:
       - name: Set up Python environment
         uses: actions/setup-python@v5
         with:
-          python-version: "3.11"
+          python-version: "3.8"
 
       - name: Update any pinned dependencies
         env: