Remove outdated README (#367)

# Description The only script described in the README has been removed in stackabletech/docker-images@65236c4#diff-2718f29b4b0d0482fa9f95369364c39f3e502f856ae62d571430c0a7784fce14 so I assume this file can go Co-authored-by: Lars Francke <lars.francke@gmail.com>

Author: lfrancke