Stop naming every palette in the credit line

The hint under the theme picker listed the third-party palettes by name.
That sentence is translated into nine languages, so every palette added
meant rewriting it, retranslating it nine times, and leaving the previous
version behind as a stale key nothing looks up.

It now describes the rule instead of enumerating the cases: a palette
named after another project is that project's work, used under its own
licence. True of the four here, true of the next one, and true without
saying "MIT" for a palette that might not be. The names are already in
Settings beside each swatch and in NOTICE with their copyright lines,
which is where a credit belongs.

Swapped rather than added in all nine catalogues, so the old key is gone
rather than left stale: 1,255 of 1,279 translated per locale, unchanged,
and the 41 pre-existing stale keys are neither added to nor cleaned up
here.

web/src/locales/ja.ts

@@ -1119,7 +1119,7 @@ export const catalog: Catalog = {
     "Date received": "受信日時",
     "Date sent": "送信日時",
     "Day view": "日表示",
-    "Dracula, Gruvbox, Rosé Pine and Tokyo Night are the work of their own projects and are used under the MIT licence; the shades between their published colours are derived, and every one of them is checked for contrast. The accent colour below still applies over any of them.": "Dracula、Gruvbox、Rosé Pine、Tokyo Night はそれぞれのプロジェクトの成果物で、MIT ライセンスのもとで利用しています。公開された色の中間の階調は派生させたもので、いずれもコントラストを確認しています。下のアクセントカラーはどの配色の上にも適用されます。",
+    "Palettes named after another project are that project's work, used under its own licence; the shades between their published colours are derived, and every one is checked for contrast. The accent colour below still applies over any of them.": "他のプロジェクトの名前が付いたパレットは、そのプロジェクトの成果物であり、そのプロジェクト自身のライセンスのもとで使用しています。公開されている色の中間の階調は派生させたもので、いずれもコントラストを検証しています。下のアクセントカラーは、どのパレットの上にも適用されます。",
     "Earlier": "これより前",
     "Every folder": "すべてのフォルダー",
     "Everyone addressed will receive this.": "宛先の全員がこれを受け取ります。",