给定一个电子邮件，删除其中的所有附件，仅保留正文。 
邮件内容: 

Dear all, 

Please find attached the agenda for the upcoming meeting. 

Best regards, 
John 

附件: "Agenda.docx"
删除邮件中的附件，仅保留正文。正文为：

Dear all, 

Please find attached the agenda for the upcoming meeting. 

Best regards, 
John