Update account cancellation documentation and email templates

[hh0592821]

This pull request updates the documentation for account deletion to clarify the application process, improve communication instructions, and update the email template guidance. The most important changes are summarized below:

Account deletion process improvements:

• Clarified that account deletion requests are generally processed in batches every 2–3 weeks, and that users should not send multiple emails or urge for faster processing.
• Added that for qualifying requests, a confirmation email will be sent, and users should check their inbox or spam folder.
• Provided instructions for canceling a deletion request by sending a cancellation email to the same address.

Email instructions and template updates:

• Updated the instructions to provide a direct link to an email template for deletion requests, and clarified the recipient email address.
• Removed the old direct-send email link and streamlined the email submission instructions.