chore: update (Japanese) translation

Translate-URL: https://librescore.ddns.net/projects/librescore/dl-librescore/ja/

Author: Thomas Winkler

src/i18n/ja.json

@@ -9,7 +9,7 @@
     "cli_usage_hint": "",
     "button_parent_not_found": "",
     "unknown_button_list_mode": "",
-    "cli_example_url": "",
+    "cli_example_url": "URL先のMP3ファイルを指定のフォルダーにダウンロードする",
     "path_to_folder": "",
     "path_to_file": "",
     "cli_example_folder": "",