CI: switch to actions/checkout@v2

Author: XhmikosR

.github/workflows/test.yml

@@ -16,7 +16,7 @@ jobs:
 
     steps:
       - name: Clone repository
-        uses: actions/checkout@v1
+        uses: actions/checkout@v2
 
       - name: Set Node.js version
         uses: actions/setup-node@v1