Assuming that Automatic Updates are enabled - temporarily disable Automatic Updates in iPad settings:
Settings > General > Software Update > Automatic Updates
Next, perform a forced-restart of your iPad:
Force restart iPad (models with Face ID or with Touch ID in the top button)
If your iPad doesn’t have the Home button, do the following:
- Press and quickly release the volume button nearest to the top button.
- Press and quickly release the volume button farthest from the top button.
- Press and hold the top button.
- When the Apple logo appears, release the top button.
Force restart iPad (models with the Home button)
Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.
After restart, you can re-enable Automatic updates should you choose to do so. The red update notification badge should now have cleared.