Update GH actions cache

Author: dadoonet

.github/workflows/pr.yml

@@ -18,7 +18,7 @@ jobs:
         java-version: '17'
         distribution: 'adopt'
     - name: Cache Maven packages
-      uses: actions/cache@v2
+      uses: actions/cache@v4
       with:
         path: ~/.m2
         key: ${{ runner.os }}-m2-${{ hashFiles('**/pom.xml') }}