Update actions/cache action to v4

Author: renovate[bot]

.github/workflows/maven.yml

@@ -25,7 +25,7 @@ jobs:
         java: [ 8, 11, 17 ]
     steps:
     - uses: actions/checkout@v2.7.0
-    - uses: actions/cache@v2.1.8
+    - uses: actions/cache@v4.2.0
       with:
         path: ~/.m2/repository
         key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}