Hello.
Previously there was not any provision to change the centre of JEE mains exam but still as the latest notification is given by national test agency on 9 April 2020, according to this notification now you are able to change your exam centre for JEE mains exam 2020 , this facilities provided to you because of the global crisis of covid-19 because of which many of the students are  stuck in different places, so we'll now you can change your centre from Delhi to Patna..
Best of luck.