Removed "Without systemd (Older Linux Distributions)"
Removed "Without systemd (Older Linux Distributions)"

Inline with the goal of:
1. Shortening the verbosity of the page
2. The declared "focus on current and prior distribution" (i.e. everything "in focus" uses `systemd`)
rabbitmq/rabbitmq-website,rabbitmq/rabbitmq-website,rabbitmq/rabbitmq-website,rabbitmq/rabbitmq-website,rabbitmq/rabbitmq-website