Drop python3.5 and python3.6

Author: Stonesjtu

.github/workflows/test.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ['3.5', '3.6', '3.7', '3.8']
+        python-version: ['3.7', '3.8']
 
     steps:
     - uses: actions/checkout@v2