chore(action): 💚 make ci work well for python3.6

Author: MerleLiuKun

.github/workflows/test.yaml

@@ -8,7 +8,7 @@ on:
 
 jobs:
   test:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     strategy:
       matrix:
         python-version: ['3.6', '3.7', '3.8', '3.9', '3.10']