(Reuters) – Shares of Warner Bros Discovery Inc rose on Monday, the first trading day of the media and streaming firm formed from the $43-billion merger of Discovery Inc and assets of AT&T Inc. Warner Bros Discovery shares were up 0.8% at $24.62, while AT&T stock climbed 2% to $18.62 before the bell. AT&T and Discovery set out to create a standalone media business in May last year and the deal closed on Friday, with the new business housing channels including HBO, CNN and the Discovery Channel as well as franchises like “Batman” and “Harry Potter”. The company, which also owns streaming servic…