Update rsnapshot_backup.md for 10

[sspencerwire]

• show installation steps and results as in 10
• add tested with 10.0 in meta
• some grammar and passive voice cleanup
• some sentence simplification
• retain source build instructions (works fine with EPEL on 10-but having the source build option there does not hurt)
• other minor corrections and updates

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 e16c37f:

Number of broken URLs: 4

URL,RESULT,FILENAME
 https://ftp.gnu.org/gnu/hello/hello-2.12.tar.gz,failed,labs/systems_administration_I/lab7-software_management.md
 http://$(hostname):8080,failed,guides/repositories/pulp_fetch_upload.md
 http://your_ip,failed,guides/cms/mediawiki.md
 https://repocompare.rockylinux.org,failed,release_notes/8_5.md