[cli] Remove beta warning for vercel build (vercel#7991)

This removes the `(beta)` output from `vercel build` as we move towards stability.

![image](https://user-images.githubusercontent.com/9113740/174356399-65f3d6bb-a241-49c8-9edb-167b25d6fa44.png)

Author: leerob

packages/cli/src/index.ts

@@ -172,7 +172,8 @@ const main = async () => {
   //  * a subcommand (as in: `vercel ls`)
   const targetOrSubcommand = argv._[2];
 
-  const betaCommands: string[] = ['build'];
+  // Currently no beta commands - add here as needed
+  const betaCommands: string[] = [''];
   if (betaCommands.includes(targetOrSubcommand)) {
     console.log(
       `${chalk.grey(