Update actions/checkout action to v2.4.2

Author: renovate-bot

.github/workflows/maven.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v2.3.4
+    - uses: actions/checkout@v2.4.2
     - name: Set up JDK 1.8
       uses: actions/setup-java@v2.1.0
       with: