upgrade checkout action (#316)

Author: willarmiros

.github/workflows/pr-build.yml

@@ -23,7 +23,7 @@ jobs:
             coverage: true
     steps:
       - name: Checkout Repository
-        uses: actions/checkout@v1
+        uses: actions/checkout@v2
 
       - name: Setup java
         uses: actions/setup-java@v1