Remove (legacy) LetsEncrypt email field

[nihalgonsalves]

What problem will this feature address?

• LetsEncrypt email notifications have ended as of June 4, 2025 – https://letsencrypt.org/2025/01/22/ending-expiration-emails
• The UI still requires the email field: LetsEncrypt email is required when certificate type is letsencrypt

Describe the solution you'd like

Remove the email field for LetsEncrypt

Describe alternatives you've considered

An alternative is to use a placeholder email @example.com since this is not used by LetsEncrypt anymore

Additional context

Happy to create a PR if you agree with the removal!

Will you send a PR to implement it?

Maybe, need help