build: Update actions/checkout action to v2.4.0 (#64)

Co-authored-by: Renovate Bot <bot@renovateapp.com>

Author: renovate[bot]

.github/workflows/build.yml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout Repository
-        uses: actions/checkout@v2.3.4
+        uses: actions/checkout@v2.4.0
       - name: Validate Gradle Wrapper
         uses: gradle/wrapper-validation-action@v1.0.4
       - name: Setup Java