Let zpretty ignore french.html test file

[mauritsvanrees]

It would be good to keep the original non-ascii characters here in french.html. They are needed for checking a regression. See my commit 60360b3 from 2020.
Can we let zpretty ignore this file, or maybe this directory?

Originally posted by @mauritsvanrees in #217 (comment)

Alternatively: change this to a different way of checking this, without needing a template that gets checked by zpretty.