[Feature Request]: Add warning in help message that `--dry-run` defaults to Let's Encrypt

### What problem does this feature solve or what does it enhance?

I was reviewing `certbot -h` to discover if there's a way to force certbot to renew a certificate immediately, and saw `--dry-run`
I ran `certbot renew --dry-run` expecting certbot to attempt a dry-run against the server I had configured when running `certbot certonly` only to discover that it attempts to communicate with letsencrypt.
Luckily that was blocked due to network config.

I did eventually find the note in https://eff-certbot.readthedocs.io/en/latest/using.html#changing-the-acme-server but I would expect something that important to be in the help.

### Proposed Solution

Add text to the help section for `--dry-run` to clarify that you must provide `--server` if you want it to use a custom server.

### Alternatives Considered

_No response_