When updates are "Managed by your system administrator" this implies that the servers are being configured for updates by group policy or a local WSUS server or Google cloud services.
Things to check, if the servers are domain joined look at the group policy settings with GPRESULT /R
See This answer relating to how to check for WSUS servers
https://superuser.com/questions/189704/how-can-i-check-if-a-computer-is-configured-to-use-wsus
And on Google cloud instances try the following:
On the Windows Server instance, open a PowerShell terminal as an
administrator. Run the googet remove command to remove the package:
PS C:> googet remove google-compute-engine-auto-updater Optionally,
you can reinstall the package to enable automatic component updates:
On the Windows Server instance, open a PowerShell terminal as an
administrator. Run the googet install command to install the package:
PS C:> googet install google-compute-engine-auto-updater
Alternatively, you can disable the updates by setting the
disable-agent-updates value to true in project or instance custom
metadata. The metadata value disables updates without removing the
package or the task.