LibreNMS current version requirements and changes

[sspencerwire]

• Since the document has now been tested with all versions of Rocky Linux, the meta was updated to include the tested versions
• Sections for iptables have been removed and replaced with firewalld instructions
• Since PHP 8.1 is now the minimum supported version, added sections on using the REMI repository and installing php81
• documentation updated for the correct path for the php81 packages and symbolic links were added where appropriate for the php binary itself
• Added separate composer install section
• corrected multiple single-line code blocks with multi-line code blocks

Author checklist (Completed by original Author)

• Contribution a good fit for the Rocky project? Title and Author MetaTags inserted ?
• Is this a non-English contribution?
• If applicable, steps and instructions have been tested to work on a real system
• Did you perform an initial self-review to fix basic typos and grammatical correctness

Rocky Documentation checklist (Completed by Rocky team)

• 1st Pass (Check that document is good fit for project and author checklist completed)
• 2nd Pass (Technical Review - check for technical correctness)
• 3rd Pass (Basic Editorial Review)
• 4th Pass (Detailed Editorial Review and Peer Review)
• Final pass/approval (Final Review)

[sspencerwire]

@EzequielBruni If you have a little time, can you give this the once over? I spent all day testing and re-writing the procedure to make sure it works for all Rocky versions, and in the process made a bunch of changes, including removing iptables rules and substituting in firewalld rules. For the most part, the words should be OK, but I won't swear that I've not misspelled something while doing this. Thanks in advance!