Added secure boot step for NVIDIA drivers

[jay3d]

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 53d588d:

Number of broken URLs: 4

URL,RESULT,FILENAME
 https://regexr.com/,failed,books/sed_awk_grep/1_regular_expressions_vs_wildcards.md
 https://www.stigviewer.com/stig/red_hat_enterprise_linux_8/,failed,books/disa_stig/disa_stig_part1.md
 https://www.stigviewer.com/stig/web_server/,failed,books/disa_stig/disa_stig_part3.md
 http://$(hostname):8080,failed,guides/repositories/pulp_fetch_upload.md

[sspencerwire]

Thank you @jay3d

[sspencerwire]

@all-contributors add @jay3d for content

[allcontributors]

@sspencerwire

I've put up a pull request to add @jay3d! 🎉