Use checkout v2 for release github action.

Author: marc0der

.github/workflows/release.yml

@@ -10,7 +10,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v2
     - name: Run tests
       run: ./gradlew clean test --info
     - name: Generate build number