The recent upgrade did not deal with obsolete conffiles properly.
Please use the dpkg-maintscript-helper support provided by
dh_installdeb to remove these obsolete conffiles on upgrade.

https://www.debian.org/doc/debian-policy/ch-files.html#s-config-files
https://manpages.debian.org/man/1/dh_installdeb

This bug report brought to you by adequate:

https://bonedaddy.net/pabs3/log/2013/02/23/inadequate-software/

   $ p=openjdk-11-jre-headless ; adequate $p ; dpkg-query -W -f='${Conffiles}\n' $p | grep obsolete
   openjdk-11-jre-headless:amd64: obsolete-conffile /etc/java-11-openjdk/security/blacklisted.certs
   openjdk-11-jre-headless:amd64: py-file-not-bytecompiled /usr/share/gdb/auto-load/usr/lib/jvm/java-11-openjdk-amd64/jre/lib/server/libjvm.so-gdb.py
    /etc/java-11-openjdk/security/blacklisted.certs 19e78890d61c0dfc65b291341c08beba obsolete