As you now have a Pro License, go to the License Manager.
Log in with your credentials that were sent in the email you received with your license activation key. The user group is User (with a capital U).
Go to the License tab, then the Server tab.
Scroll down to Updates Mode.
Change that to Never.
Click the Save Settings button.
You will no longer receive update notifications, but you can still update manually by downloading the latest version from the Release History.