Don't check for webhooks on non-production instances

I used to handle this in an extension, but since 6.5 changed the name of the check to something dynamic, I figured it was time to push this upstream.

When I get a moment I'll do the same on the Auth.net extension, which is a bit more pernicious since it creates the webhooks without asking.

@JonGold Makes sense. I'll let 6.5 settle a bit and then merge!

I'm more than happy to review a PR that adds webhooks for authnet in a similar way to Stripe does (ie. with the form and button).

Great. I'm tracking down some other bugs in the checks - expect more PRs shortly!

merged