See as per the official website of Gujrat Board, there is no such rules and regulations available for changing the stream. You should contact your school/Institution in order to know if its possible or not. Even, if its possible, then also you have to cancel your registration and then get registered again with the Arts combinations.

For the official website of Gujrat Higher Secondary Board, consider visiting the link below:

https://www.gsebeservice.com/

I hope this helps. Wish you a great eve!