Update GitHub Actions to v4

Author: Aleksandar Damjanovic

.github/workflows/maven.yml

@@ -14,15 +14,9 @@ jobs:
       matrix:
         java: [ 8 ]
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions/cache@v1
-        with:
-          path: ~/.m2/repository
-          key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
-          restore-keys: |
-            ${{ runner.os }}-maven-
+      - uses: actions/checkout@v4
       - name: Set up JDK ${{ matrix.java }}
-        uses: actions/setup-java@v2
+        uses: actions/setup-java@v4
         with:
           java-version: ${{ matrix.java }}
           distribution: 'zulu'