prerm is in gnome-icon-theme-gartoon-redux 1.10-0ubuntu2.
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 | #!/bin/sh
set -e
rm -f /usr/share/icons/GartoonRedux/icon-theme.cache
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