In general, this is impossible.
First off, you can't prevent an extension from executing a Content Script on your site.
Second, there are both standard and hacky ways of disabling autofill, but those extensions are specifically designed to bypass as many of those restrictions as possible, trying to guess what the real fields to remember are. This is an escalating arms race, and you don't want to get involved.
Lastly, comments raise a valid point - this is client software (browser configured in a certain way) talking to your server. How that client software works is not your concern, and not in your control. What if by using tricks to confuse autofillers you are seriously hurting accessibility of your site? What if you're annoying users?