Fix flights-map popup showing raw i18n key

The arrival-city popup called t('FLIGHTS-MAP.BUY-TICKET') but the key
in every locale file is FLIGHTS-MAP.BUY_TICKET_BTN (it was renamed
earlier). Map popups rendered the raw key 'FLIGHTS-MAP.BUY-TICKET'
instead of 'Купить билет'. Point the call at the existing key.

src/features/flights-map/components/FlightsMapStartPage.tsx

@@ -248,7 +248,7 @@ export const FlightsMapStartPage: FC = () => {
     <div class="popup-header-test"><span>${escapeHtml(arrCity.name)}</span></div>
     <div style="text-align:center;">
       <a href="${buyUrl}" target="_blank" class="popup-buy-ticket">
-        ${t("FLIGHTS-MAP.BUY-TICKET")}
+        ${t("FLIGHTS-MAP.BUY_TICKET_BTN")}
       </a>
     </div>
   `;