fix: remove unused --verbose option from start command

[liamjones]

Summary:

While investigating #1391 I discovered that the start command had a --verbose option that didn't do anything. You do get extra logging with --verbose but this comes from the parent react-native command, where it is already documented.

I had a look through the metro functions being called to see if verbose was meant to be passed to one of them and had been missed but couldn't find anywhere it would be relevant. The only one I could see that it would potentially apply to is the loadMetroConfig call. While loadMetroConfig doesn't document a verbose parameter of its own, it calls loadConfig in the metro-config package which does take a verbose parameter. However, all that does is kill the reporter if verbose === false (see https://github.com/facebook/metro/blob/master/packages/metro-config/src/loadConfig.js#L256), which would mean you get no output from the start command whatsoever. Currently, the loadMetroConfig code is reliant on the fact that verbose is undefined when calling loadConfig so its custom reporter isn't overwritten.

Test Plan:

• Ran react-native start --verbose before making this change and observed extra logging
• Removed verbose option from the start command
• Ran react-native start --verbose again and still observed extra logging

[thymikee]

Thanks for the cleanup!

[grabbou]

Nice catch, thanks!