Update `Japanese` translation

Currently translated at 5.3% (29 of 540 strings)

Translation: Wiki-Bot/Discord
Translate-URL: https://weblate.frisk.space/projects/wiki-bot/discord/ja/

i18n/ja.json

@@ -41,7 +41,7 @@
             " "
         ],
         "help": [
-            "",
+            "ヘルプ",
             "",
             "",
             "",