390 implement new interview content on candidate mailer

[YoniF1]

Context

New copy for new interview email sent to candidates

Changes proposed in this pull request

• Change content, update tests

Guidance to review

Visit /rails/mailers/candidate_mailer/new_interview and verify content follows changes specified in google doc

Link to Trello card

https://trello.com/c/0KQuLHve/390-implement-new-interview-content-on-candidate-mailer

Things to check

• If the code removes any existing feature flags, a data migration has also been added to delete the entry from the database
• This code does not rely on migrations in the same Pull Request
• If this code includes a migration adding or changing columns, it also backfills existing records for consistency
• If this code adds a column to the DB, decide whether it needs to be in analytics yml file or analytics blocklist
• API release notes have been updated if necessary
• Required environment variables have been updated added to the Azure KeyVault