remove unused function

app.ts

@@ -116,20 +116,6 @@ async function getTransactionDetail(txHash: string, user: string) {
     return quer.transactionsList[0].payload.reducedPayload.commandsList[0].transferAsset;
 }
 
-function getArea(extent: Array<Array<number>>): number {
-
-    let y1 = extent[0][1];
-    let y4 = extent[3][1];
-
-    let x1 = extent[0][0];
-    let x2 = extent[1][0];
-
-    let height = Math.abs(y1 - y4);
-    let width = Math.abs(x1 - x2);
-
-    return height * width;
-}
-
 function getPrice(area: number) : number {
     return area * PRICE_MODIFIER;
 }