Remove cron daily backup

It was added in 2010 (#554170) as a split off from a previous cron
job.  I haven't seen an arguement for why it's useful to keep.

Depending on when a mistake occurs in one of the files it backups
it will provide variable recovery time of 0 to 24hours.

debian/passwd.cron.daily

@@ -1,9 +0,0 @@
-#!/bin/sh
-
-cd /var/backups || exit 0
-
-for FILE in passwd group shadow gshadow; do
-        test -f /etc/$FILE              || continue
-        cmp -s $FILE.bak /etc/$FILE     && continue
-        cp -p /etc/$FILE $FILE.bak && chmod 600 $FILE.bak
-done