Update from actions/cache@v2 to actions/cache@v4

Author: kwvanderlinde

.github/workflows/verify-build.yml

@@ -33,13 +33,13 @@ jobs:
       with:
         java-version: ${{ matrix.java }}
     - name: Cache Gradle
-      uses: actions/cache@v2
+      uses: actions/cache@v4
       with:
         path: |
           ~/.gradle/caches
           ~/.gradle/wrapper
-        key: ${{ runner.os }}-gradle-v2-${{ hashFiles('**/*.gradle*', '**/gradle-wrapper.properties') }}
+        key: ${{ runner.os }}-gradle-v4-${{ hashFiles('**/*.gradle*', '**/gradle-wrapper.properties') }}
         restore-keys: |
-          ${{ runner.os }}-gradle-v2-
+          ${{ runner.os }}-gradle-v4-
     - name: Build with Gradle
       run: ./gradlew build