Update firmware guidelines for deployment

[sirajyasin]

Added notes on iDRAC firmware downgrade limitations and best practices for component firmware alignment.

[prmerger-automator]

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[learn-build-service-prod]

Learn Build status updates of commit 9c28576:

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[v-dirichards]

@JAC0BSMITH

Can you review the proposed changes?

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[Copilot]

Pull request overview

This PR enhances the firmware deployment documentation by adding important notes about iDRAC firmware downgrade limitations and best practices for component firmware alignment. These additions provide critical guidance for operators preparing servers for Operator Nexus platform deployment.

Key changes:

• Documents known limitations in iDRAC versions earlier than 7.20.30.50 regarding firmware downgrade support
• Adds best practice recommendations to prevent BIOS corruption during firmware alignment by ensuring component firmware versions are at or below target versions

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[learn-build-service-prod]

Learn Build status updates of commit 77c1a4b:

✅ Validation status: passed

File	Status	Preview URL	Details
operator-nexus/howto-platform-prerequisites.md	✅Succeeded

For more details, please refer to the build report.