Update librenms_monitoring_server.md - php dnf module variant

[Atroskelis]

Installing php81 adds php81 as a command and does not replace the classic php command.

Thus in my case the dependency script failed as there is no php command.

in the official librenms documentation for centos 8, they use dnf module to replace the php install with the remi one.

I consider this case similar here.

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 d06b176:

Number of broken URLs: 1

URL,RESULT,FILENAME
 https://azuremarketplace.microsoft.com/en-us/marketplace/apps/resf.rockylinux-aarch64,failed,guides/cloud/migration-to-new-azure-images.md

[sspencerwire]

Thanks very much for your input @Atroskelis!

[sspencerwire]

@all-contributors please add @Atroskelis for content

[allcontributors]

@sspencerwire

I've put up a pull request to add @Atroskelis! 🎉