“Reliable Sources,” the media-news program that has been on CNN since 1993, is the latest piece of content to go on the chopping block under the cost-cutting regime of Warner Bros. Discovery. The show, which has grown from a dusty public affairs program in its earliest days to a lean-forward show that often took on Fox News and President Donald Trump under former CNN chief Jeff Zucker, will broadcast its last episode on Sunday, August 21. Its anchor, Brian Stelter, will leave the company. “We appreciate his contributions to the network and wish him well as he embarks on new...