Remove ZeroSSL from Caddyfile

[afeiszli]

Describe your changes

There is an ongoing issue with ZeroSSL causing rate limiting: cert-manager/cert-manager#5867

We should revert from ZeroSSL until this issue is resolved.

Provide Issue ticket number if applicable/not in title

#2129

Provide testing steps

Checklist before requesting a review

• My changes affect only 10 files or less.
• I have performed a self-review of my code and tested it.
• If it is a new feature, I have added thorough tests, my code is <= 1450 lines.
• If it is a bugfix, my code is <= 200 lines.
• My functions are <= 80 lines.
• I have had my code reviewed by a peer.
• My unit tests pass locally.
• Netmaker is awesome.

[ghost]

Thank!