updated publish action to fix deprecation warnings

.github/workflows/python-package.yml

@@ -13,9 +13,9 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@main
     - name: Set up Python
-      uses: actions/setup-python@v2
+      uses: actions/setup-python@main
       with:
         python-version: '3.x'
     - name: Install dependencies