This same "Tap to update" message appears repeatedly on my launcher screen, right over the app tray icon, without the keyboard being active. I've tapped it but it doesn't stop it from coming back at some seemingly random future time. It can pop up multiple times a day and it's not clear what's being updated. As best I can tell this didn't start until I updated my Nexus 5X from Android 7.1.2 to 8.1.0, but of course various apps have also been updated. This makes it difficult to point at a single piece of software. Whatever it is, I'd really like to make it stop!