chore(ui): shorter WSJT-X highlight wording

The main hint named three fixed colours, which stopped being true the
moment the operator could choose them. And the paragraph under "Mark
stations already worked" explained a trade-off nobody reads standing at
the radio; the switch says what it does.

frontend/src/components/UDPIntegrationsPanel.tsx

@@ -299,10 +299,7 @@ export function UDPIntegrationsPanel({ onError }: Props) {
         <label className="flex items-start gap-2 text-sm cursor-pointer max-w-2xl pl-6">
           <Checkbox checked={hlWorked}
             onCheckedChange={(c) => { setHlWorked(!!c); void SetWsjtHighlightWorked(!!c); }} />
-          <span>
-            {t('udpp.hlWorked')}
-            <span className="block text-[11px] text-muted-foreground">{t('udpp.hlWorkedHint')}</span>
-          </span>
+          <span>{t('udpp.hlWorked')}</span>
         </label>
       )}
       <label className="flex items-start gap-2 text-sm cursor-pointer max-w-2xl">