editing 16-about-systemd.md

[sspencerwire]

• some sentence simplification
• replacement of passive voice phrases where possible
• since systemd is a daemon (and yes a suite of programs as well) I believe it needs to be consistently entered in lower case, rather than "Systemd" and it needs to be consistently in code back tics too (systemd) this might be a judgement call on my part. I made an exception for quoted content.
• indented bulleted items need to be 4 spaces, rather than 2
• for the most part (unless complete sentences) bulleted items do not need punctuation or capitalization
• remove some errant spaces at the end of lines
• remove some tab characters within the examples for the unit file
• replaced the "[" and "]" with ++open-bracket++ and ++close-bracket++ respectively
• Where System V and SystemV are noted, replaced with the more commonly accepted SysV for uniformity
• ensure fenced code blocks have titles (example bash or text)

Author checklist (Completed by original Author)

• Good fit for the Rocky Linux project? Title and Author Metatags inserted ?
• If applicable, steps and instructions have been tested to work
• Initial self-review to fix basic typos and grammar completed

Rocky Documentation checklist (Completed by Rocky team)

• 1st Pass (Document is good fit for project and author checklist completed)
• 2nd Pass (Technical Review - check for technical correctness)
• 3rd Pass (Detailed Editorial Review and Peer Review)
• Final approval (Final Review)

[github-actions]

Test results for a056e6c:

Number of broken URLs: 3

URL,RESULT,FILENAME
 https://modoboa.org/en/,failed,guides/email/01-email-system.md
 https://www.ossec.net/docs/,failed,guides/web/apache_hardened_webserver/ossec-hids.md
 https://www.linode.com/docs/guides/beginners-guide-to-lxd-reverse-proxy,failed,guides/containers/lxd_web_servers.md