Dear maintainer,
If you upgrade unclutter to 8-25 and also install unclutter-startup,
then the file /etc/X11/Xsession.d/90unclutter remains under the
ownership of bin:unclutter, and so is considered an obsolete conffile
(as shown by e.g. `dpkg-query --show
--showformat='\${Package}\\n\${Conffiles}\\n' | grep obsolete`).
I guess that ownership of the conffile needs to be transferred to
unclutter-startup somehow.