Disable Filscan querying in favor of using Filfox exclusively

Filfox has a convenient API for retrieving fee info on a message.
Filscan doesn't have an known API for getting the fee amounts without
figuring out how to calculate the fee amounts from four or five fee
related fields on a Filecoin message.

src/filecoin/FilecoinEngine.ts

@@ -343,7 +343,7 @@ export class FilecoinEngine extends CurrencyEngine<
       }
 
       const scanners = [
-        this.scanTransactionsFromFilscan(addressString, handleScan),
+        // this.scanTransactionsFromFilscan(addressString, handleScan),
         this.scanTransactionsFromFilfox(addressString, handleScan)
       ]