Update actions/cache to v4

Author: devgianlu

.github/workflows/maven.yml

@@ -31,7 +31,7 @@ jobs:
           GPG_SECRET_KEYS: ${{ secrets.GPG_SECRET_KEYS }}
           GPG_OWNERTRUST: ${{ secrets.GPG_OWNERTRUST }}
       - name: Cache local Maven repository
-        uses: actions/cache@v2
+        uses: actions/cache@v4
         with:
           path: ~/.m2/repository
           key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}