magento/magento2#675: [Test coverage] Generate customer token

- code style fix

Author: lenaorobei

dev/tests/api-functional/testsuite/Magento/GraphQl/Customer/GenerateCustomerTokenTest.php

@@ -107,7 +107,8 @@ public function dataProviderInvalidCustomerInfo(): array
      * @param string $password
      * @return string
      */
-    private function getQuery(string $email, string $password) : string {
+    private function getQuery(string $email, string $password) : string
+    {
         return <<<MUTATION
 mutation {
 	generateCustomerToken(