Revert "unixPB: Install rng-tools to fix low entropy (#3145)"

[sxa]

This reverts commit a2989df.

https://ci.adoptium.net/job/centos7_docker_image_updater/373/execution/node/79/log/ is showing this on CentOS7:

#13 1259.1 TASK [rngd : Start and enable "rngd" service (Fedora)] *************************
#13 1259.6 fatal: [localhost]: FAILED! => {"changed": false, "msg": "Could not find the requested service rngd: "}

Checklist

• commit message has one of the standard prefixes
• faq.md updated if appropriate
• other documentation is changed or added (if applicable)
• playbook changes run through VPC or QPC (if you have access)
• VPC/QPC not applicable for this PR
• for inventory.yml changes, bastillion/nagios/jenkins updated accordingly

[steelhead31]

LGTM