1. Turn your phone off and then on again. This will reset everything and you should be able to update then.
2. Completely close out the App Store app. On older versions of iOS (pre iPhone X) you do this by double-clicking the home button and swiping up on an app. On the iPhone X, you can swipe up from the very bottom to show all the apps, then swipe up to close it out. After the App Store is closed out, re-open and you'll be able to update the Food Network Kitchen app.