postrm is in open-vm-tools-dkms 2:10.0.7-3227872-2ubuntu1.
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 | #!/bin/sh
set -e
case "$1" in
    remove)
        if which update-initramfs >/dev/null; then
                update-initramfs -u
        fi
    ;;
esac
 |