Feature request: Clearer messaging around authentication during `sam deploy --guided`

### Describe your idea/feature/enhancement

I used `sam init` to create a very simple `Hello World` project.

1. "Which template source would you like to use?" => 1 - AWS Quick Start Templates
2. "Choose an AWS Quick Start application template" => 1 - Hello World Example

When I go to deploy what is produced from this using `sam deploy --guided`, it asks me:

> HelloWorldFunction has no authentication. Is this okay? [y/N]

I don't know what that's in reference to, so I'm not sure if it's okay! Doing some digging, it looks like it's in reference to the API Gateway endpoint the template set up. Why did the template give me something that's not ok?

### Proposal

I would make the message around `HelloWorldFunction` having no authentication clearer. What does it mean? What's the impact of saying yes?

Or, if you gave me the template then it should be okay and you shouldn't ask, or the template should give me authentication.