minor editing of ssh_ca_key_signing.md

[sspencerwire]

• Sentence style capitalization on headers throughout
• bulleted items need not have punctuation unless they combine one or more sentences
• some minor sentence restructuring to remove passive voice
• add language context to fenced code blocks (bash)
• Markdown linters don't like the mixing of bullet items (use either - or *, but not both)
• fix a few spelling mistakes

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)

[sspencerwire]

Thank you again @hs303 !

[github-actions]

Test results for a4c4c9e:

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