Update PaypalExpressToken.php

Update PaypalExpressToken resolver to use correct input from GraphQL Schema.

Author: Liam Toohey

app/code/Magento/PaypalGraphQl/Model/Resolver/PaypalExpressToken.php

@@ -83,7 +83,7 @@ public function resolve(
     ) {
         $cartId = $args['input']['cart_id'] ?? '';
         $paymentCode = $args['input']['code'] ?? '';
-        $usePaypalCredit = isset($args['input']['paypal_credit']) ? $args['input']['paypal_credit'] : false;
+        $usePaypalCredit = isset($args['input']['use_paypal_credit']) ? $args['input']['use_paypal_credit'] : false;
         $usedExpressButton = isset($args['input']['express_button']) ? $args['input']['express_button'] : false;
         $customerId = $context->getUserId();