User Configuration > Administrative Templates > Microsoft Word 2016 > File Tab > Check Accessibility
User
HKCU\software\policies\microsoft\office\16.0\word\accchecker
This policy setting prevents the Accessibility Checker from verifying that objects such as images and shapes contain alt text. If you enable this policy setting, the Accessibility Checker will be prevented from verifying that objects such as images and shapes contain alt text. If you disable or do not configure this policy setting, objects will be checked for alternative text and any issues will appear in the Accessibility Checker.