chore(arns): change reference gateway to arweave.net

This is the production arns resolver and what observers validate against - https://github.com/ar-io/ar-io-observer/blob/develop/src/config.ts#L62-L65.

src/utils/observations.ts

@@ -6,7 +6,7 @@ import { ArNSAssessment, Assessment, OwnershipAssessment } from '@src/types';
 import { arrayBufferToBase64Url, fetchWithTimeout } from '.';
 
 const NAME_PASS_THRESHOLD = 0.8;
-const REFERENCE_GATEWAY_FQDN = 'ar-io.dev';
+const REFERENCE_GATEWAY_FQDN = 'arweave.net'; 
 
 export const assessOwnership = async (
   gateway: AoGatewayWithAddress,