Remove `ServerMaintenanceNeeded` and `ServerMaintenanceApproval` annotations

[defo89]

Summary

This is follow up for #615 and #618

• Having ServerMaintenanceNeeded / ServerMaintenanceApproval both as label and annotation on ServerClaim was needed for the transition phase.
• We should remove the annotation since CCM operates on the label.

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🔗 Related PRs

#564 - Improve watch setup in ServerMaintenance reconciler [merged]
#581 - Transition Server to Maintenance in case of pending BIOS settings exist [merged]
#595 - Fix Server UUID print column [merged]
#599 - Improved internal code structure of the bmc package [merged]
#615 - Set maintenance needed label on ServerClaim [closed]

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