Update actions/upload-artifact action to v6

Author: renovate[bot]

.github/workflows/maven.yml

@@ -30,7 +30,7 @@ jobs:
       - name: "Target Stage"
         run: mkdir staging && cp target/*.jar staging
       - name: "Upload artifact"
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: artifact
           path: staging