А вот так достаточно корректно? «Hi! If you don't have any more work for me, I'd rather close the contract. Now only the milestone is closed.
I hope for your feedback. Thank you!»
Я обычно пишу "Could you please close the contract and leave feedback. I'll do the same for you too. Thank you in advance" или вот так
Hi "name",
Thank you for your reply
Yes, I think it is time to Close existing Contract.
This action is only for the formal purpose. Please do not take it seriously.
At any time, we can renew our cooperation - you can use the "Rehire" button.
I'll give you 5-star mark, with positive feedback. I hope that you will too.
Your positive feedback will be very helpful for me.
Looking forward to your understanding and future cooperation.
Best regards,
"Your name"!