workflow fix

Author: hownowstephen

.github/workflows/main.yml

@@ -4,14 +4,14 @@ on: [ push ]
 
 jobs:
   build:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     strategy:
       matrix:
         python: [ '3.6', '3.7', '3.8','3.9' ]
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - name: Set up Python
-      uses: actions/setup-python@v2
+      uses: actions/setup-python@v5.6.0
       with:
         python-version: ${{ matrix.python }}
     - name: install dependencies for the minor version