Meta: (test.yml) Use checkout@v2

Author: alphapapa

.github/workflows/test.yml

@@ -44,7 +44,7 @@ jobs:
       with:
         version: ${{ matrix.emacs_version }}
 
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v2
 
     - name: Install sandbox script
       run: |