web-ui: Add production api address

web-ui/src/environments/environment.prod.ts

@@ -1,7 +1,6 @@
 export const environment = {
   production: true,
   api: {
-    // TODO: replace with the correct value
-    url: 'http://localhost:9000'
+    url: 'https://xsnexplorer.io/api'
   }
 };