ci: upgrade actions/cache to v4 to fix deprecation warning

Author: Zorin95670

.github/workflows/maven_publish.yml

@@ -39,7 +39,7 @@ jobs:
           GPG_PRIVATE_KEY: ${{ secrets.GPG_PRIVATE_KEY }}
 
       - name: Cache Maven dependencies
-        uses: actions/cache@v2
+        uses: actions/cache@v4
         with:
           path: ~/.m2/repository
           key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}