Make consistent environment between jobs

.github/workflows/main-ci.yml

@@ -15,7 +15,7 @@ env:
 
 jobs:
   build:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
 
     steps:
       - uses: actions/checkout@v4
@@ -31,6 +31,11 @@ jobs:
           git clone --depth 1 https://github.com/anngvu/retold.git
           make
 
+      # Set up supported python.
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.10.12' 
+
       - name: Setup schematic and do another convert pass
         id: schematic-convert
         run: |