To reset or disable the new quiz option in a course, the faculty member will need to go to the course link for Settings. Then the "Features" Tab and click the green check box next to New Quizzes. Turning off New quizzes at the course level will override the ability to create quizzes of the "New Quiz" type in that course. It will not impact existing quizzes "New" or "Classic."
Canvas is continually creating new features to improve your experience. The majority of improvements will be made available as part of our regular release cycle. However, some features may change the workflow for common activities in Canvas during your current term. Because we want you to be able to learn about these features at your own pace, they’ll be placed in your Course Settings as a Feature Option. Feature Options allow you to choose when you want to enable the new feature for your course.
For more information on how to manage course features please see the article linked below:
How do I manage new features for a course?