Update the URL for the Metric Service (#8261)

The custom domain "firebase-sdk-health-metrics.com" currently
associated with the Metric Service will be deprecated eventually,
due to the acquisition of Google Domains by Squarespace.

Switching to the original URL created by Google Cloud Run (which
hosts the Metric Service) to avoid service disruption.

See b/303931111 for more details.

scripts/size_report/size_report_helper.ts

@@ -27,7 +27,7 @@ export enum RequestEndpoint {
 }
 export const runId = process.env.GITHUB_RUN_ID || 'local-run-id';
 
-const METRICS_SERVICE_URL = 'https://api.firebase-sdk-health-metrics.com';
+const METRICS_SERVICE_URL = 'https://metric-service-tv5rmd4a6q-uc.a.run.app';
 
 function constructRequestPath(requestEndpoint: string): string {
   const repo = process.env.GITHUB_REPOSITORY;