If a user is removed from the TMS Users list, the report(s) created in Schedule Center are not removed and neither will be when if the user is removed from the Contact Center (this means that the user's info is still there even when the user is removed from TMS).
However, even though the scheduled report(s) will be there, it will fail to be delivered. The screenshot below is an example of the error logged by alerts in Nova when a user is removed from TMS and Contact Center:

A user with a System Administrator role will need to edit the report in Schedule Center and update the recipient(s) to fix this issue.