fix incorrect casing of includeUsdRate option passed to CurrencyRateController

Author: adonesky1

app/scripts/metamask-controller.js

@@ -400,7 +400,7 @@ export default class MetamaskController extends EventEmitter {
       name: 'CurrencyRateController',
     });
     this.currencyRateController = new CurrencyRateController({
-      includeUSDRate: true,
+      includeUsdRate: true,
       messenger: currencyRateMessenger,
       state: {
         ...initState.CurrencyController,