update

Author: fanqingsong

.github/workflows/pytest_flake8.yml

@@ -18,7 +18,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu20.04]
+        os: [ubuntu-20.04]
         python-version: ['3.8.0', '3.9.0', '3.10.0']
 
     steps: