Try setting checkout action to v3 to resolve dubious ownership error

See these issues for more info:

* actions/checkout#1048
* actions/runner-images#6775

.github/workflows/main.yml

@@ -8,9 +8,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@master
-      with:
-        set-safe-directory: '*'
+    - uses: actions/checkout@v3
     - name: Deploy code to Lambda
       uses: denzalman/lambda-python-action@v1.1.0
       with: