Update DNF package manager documentation

[ssimpson89]

You need epel as well as CRB or PowerTools

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 158b375:

Number of broken URLs: 12

URL,RESULT,FILENAME
 https://mirrors.fedoraproject.org/metalink?repo=epel-8&arch=$basearch&infra=$infra&content=$contentdir,failed,books/admin_guide/13-softwares.md
 https://support.torproject.org/glossary/pluggable-transports/,failed,guides/proxies/tor_relay.md
 http://your_ip,failed,guides/cms/mediawiki.md
 http://$(hostname):8080,failed,guides/repositories/pulp_fetch_upload.md
 https://wiki.rockylinux.org/team/release_engineering/debranding/,failed,guides/package_management/package_debranding.md
 https://dl.rockylinux.org/pub/rocky/9.6/live/x86_64/,failed,guides/desktop/kde_installation.md
 https://www.packer.io/docs/builders/vsphere/vsphere-iso,failed,guides/automation/templates-automation-packer-vsphere.md
 https://git.launchpad.net/cloud-init,failed,guides/virtualization/cloud-init/07_contributing.md
 https://ftp.gnu.org/gnu/tar/,failed,guides/backup/tar.md
 https://andyscott.me,failed,guides/contribute/README.md
 https://ftp.gnu.org/gnu/hello/hello-2.12.tar.gz,failed,labs/systems_administration_I/lab7-software_management.md
 https://repocompare.rockylinux.org,failed,release_notes/8_5.md

[sspencerwire]

Great job @ssimpson89! One thing from a multi-language point of view, avoid contractions: i.e. "you'll" becomes "you will."

Better still, to avoid passive voice phrasing, simply state "install the epel-release first:"

Otherwise this is looking great so far. Thanks for your edit!