update actions/cache

Author: trobert

.github/workflows/MavenCI.yml

@@ -30,7 +30,7 @@ jobs:
         java-version: ${{ matrix.java-version }}
 
     - name: Cache Maven packages
-      uses: actions/cache@v2
+      uses: actions/cache@v4
       with:
         path: ~/.m2
         key: ${{ runner.os }}-m2-${{ hashFiles('**/pom.xml') }}