fixed signRegion setting for far east endpoints

Author: 77web

src/AmazonIncentivesClient.php

@@ -375,14 +375,14 @@ protected function getEndpointMetadata(?string $region): array
             case 'fe':
                 return [
                     'endpoint' => 'https://agcod-v2-fe.amazon.com',
-                    'signRegion' => 'eu-west-1',
+                    'signRegion' => 'us-west-2',
                     'signService' => 'AGCODService',
                     'signVersions' => ['v4'],
                 ];
             case 'fe-sandbox':
                 return [
                     'endpoint' => 'https://agcod-v2-fe-gamma.amazon.com',
-                    'signRegion' => 'eu-west-1',
+                    'signRegion' => 'us-west-2',
                     'signService' => 'AGCODService',
                     'signVersions' => ['v4'],
                 ];