Deploy keys are disabled for this repository

Github organisations have disabled the usage of deploy keys by default, as explained here.

If you face this error, you need to:

1. In the upper-right corner of GitHub, select your profile photo, then click Your organizations.
2. Next to the organization, click Settings.
3. In the "Access" section of the sidebar, click Member privileges.
4. Under "Deploy keys", review the information about changing the setting, click Enabled or Disabled.
5. Click Save.