use 'new' action cache version

Author: cmangeat

.github/workflows/geonetwork-docker.yml

@@ -22,7 +22,7 @@ jobs:
         java-version: 1.8
 
     - name: "Cache Maven packages"
-      uses: actions/cache@v2
+      uses: actions/cache@v3
       with:
         path: ~/.m2
         key: ${{ runner.os }}-m2-${{ hashFiles('**/pom.xml') }}