This allows unicode characters in bookmarks as metion in 11.5 form the hyperref manual. (ftp://tug.ctan.org/pub/tex-archive/macros/latex/contrib/hyperref/doc/manual.pdf)
Thanks to Holger Peters [1] for raising this issue on Twitter. I would
not have caught it otherwise because I am not using `pdflatex` to work
with the package.
[1]: https://www.holger-peters.de/