Update actions/upload-artifact action to v6

Author: renovate[bot]

.github/workflows/build.yml

@@ -26,7 +26,7 @@ jobs:
         run: ./gradlew build
 
       - name: Upload artifact
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v6
         with:
           name: alpine
           path: |