Instagram is running a new test to tell users about another app they might want to check out: Facebook. The photo sharing app is experimenting with a notice at the top of users’ feeds that encourages them to check out features that are “only available” on Facebook.“We’re testing a way to let people who have connected their Instagram accounts to Facebook know about features only available there, such as how to find a job, date online, buy and sell goods, or catch up on the latest news,” a spokesperson said in a statement.That the company is using one of its billion-user apps to promote another billion-user app might not seem to make a lot of sense, but it’s only the latest (and perhaps most aggressive) way the social network has used Instagram to drive people back to its main app. The company has been steadily bringing the two apps closer together and has been encouraging users to link their accounts. (A book published last year reported that Mark Zuckerberg was &ldquo
