Remove unneeded strings

Signed-off-by: Stefan Parviainen <pafcu@iki.fi>

src/i18n/strings/ja.json

@@ -8,7 +8,6 @@
     "Create Room": "部屋を作成",
     "Current password": "現在のパスワード",
     "Delete": "削除",
-    "Direct Chat": "対話",
     "Direct chats": "対話",
     "Display name": "表示名",
     "Enable encryption": "暗号会話開始",
@@ -26,7 +25,6 @@
     "Notifications": "通知",
     "Cancel": "取消",
     "Create new room": "新しい部屋を作成",
-    "Failed to join the room": "部屋への参加に失敗しました",
     "Room directory": "公開部屋一覧",
     "Search": "検索",
     "Settings": "設定",