fix(aws-appsync): Update aws-sdk to be the same as amplify (#458)

Author: elorzafe

packages/aws-appsync/package.json

@@ -26,7 +26,7 @@
     "apollo-link-context": "1.0.9",
     "apollo-link-http": "1.3.1",
     "apollo-link-retry": "2.2.5",
-    "aws-sdk": "2.472.0",
+    "aws-sdk": "2.518.0",
     "debug": "2.6.9",
     "graphql": "0.13.0",
     "redux": "^3.7.2",