Update actions/upload-artifact action to v6 (#278)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/gradle.yml

@@ -60,7 +60,7 @@ jobs:
 
       # https://github.com/actions/upload-artifact
       - name: Upload build artifact
-        uses: actions/upload-artifact@v5.0.0
+        uses: actions/upload-artifact@v6.0.0
         with:
           name: UltraCosmetics-GUI-Addon
           path: build/libs/UltraCosmetics-gui-addon-*.jar