postrm is in openssh-client 1:7.6p1-4ubuntu0.3.
This file is a maintainer script. It is executed when installing (*inst) or removing (*rm) the package.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22  | #!/bin/sh
set -e
case $1 in
	purge)
		# Remove all non-conffiles that ssh might create, so that we
		# can smoothly remove /etc/ssh if and only if the user
		# hasn't dropped some other files in there. Conffiles have
		# already been removed at this point.
		rm -f /etc/ssh/moduli /etc/ssh/primes
		rm -f /etc/ssh/ssh_known_hosts /etc/ssh/ssh_known_hosts2
		[ ! -d /etc/ssh ] || rmdir --ignore-fail-on-non-empty /etc/ssh
		if which delgroup >/dev/null 2>&1; then
			delgroup --quiet ssh > /dev/null || true
		fi
		;;
esac
exit 0
 |