Update wildcard pattern example in line with 2.10.0 changes to default handling of wildcard certs

I started using caddy a few days ago, and per the relevant documentation, I set up my Caddyfile as suggested in the wildcard pattern.
It worked with my first reverse proxy subdomain, but when I added the second one, I could not get it to work.

After much searching and experimenting, I discovered that the wildcard handling was changed in 2.10.0. I downgraded my container to 2.9.1, and my Caddyfile worked without any problems.

It appears that the wildcard pattern provided in the docs is no longer valid.

After looking through the release notes, I discovered caddyserver/caddy/pull/6959 in which @mholt provides documentation for the change, in particular offering the template for how the wildcard based setup should be handled now.

Please consider updating the docs to prevent other newbies having a similar experience dealing with seemingly outdated documentation.

Start with the wildcard pattern documentation page linked in the issue and review caddyserver/caddy/pull/6959 for the 2.10.0 behavior. Update the wildcard certificate example to match the current default handling, then verify that the page no longer recommends the outdated pattern.