Fix new Ahrefs audit issues: Discord redirect link and CLI reference meta descriptions - #53

Running Vale across on the following files affected by this PR:

- cli/reference/certificate.mdx
- cli/reference/domain.mdx
- contact-support.mdx

Attempting to initialize Vale linter...
Customer vale configuration detected. Attempting to sync packages...
Packages synced successfully.
Attempting to run Vale spellcheck...
Vale spellcheck completed successfully.
Checked for suggestions and found none in 852.14ms