Update location => primary region in code and backend display table.

Author: annajowang

src/commands/apphosting-backends-list.ts

@@ -7,7 +7,7 @@ import { Options } from "../options";
 import * as apphosting from "../gcp/apphosting";
 import * as Table from "cli-table3";
 
-const TABLE_HEAD = ["Backend", "Repository", "URL", "Location", "Updated Date"];
+const TABLE_HEAD = ["Backend", "Repository", "URL", "Primary Region", "Updated Date"];
 
 export const command = new Command("apphosting:backends:list")
   .description("list Firebase App Hosting backends")