Update instructions for hashing the root password for clients

[michael-riddle]

https://github.com/simp/simp-core/blob/master/build/distributions/CentOS/8Stream/x86_64/DVD/ks/pupclient_x86_64.cfg is the file in question, line 3. Simply add the path to the ruby installed with puppet /opt/puppetlabs/puppet/bin/ruby