Denying access to a previously approved OAuth App for your organization

If an organization no longer requires a previously authorized OAuth App, owners can remove the application's access to the organization's resources.

In the top right corner of GitHub, click your profile photo, then click Your profile.
On the left side of your profile page, under "Organizations", click the icon for your organization.
Under your organization name, click Settings.
In the Settings sidebar, click Third-party access.
Next to the application you'd like to disable, click .
Click Deny access.